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Review Q&A subframe crossmember bolts
What is the most difficult part to replace/repair on a car?
Depends on the car, really. However, here are some horrible examples: the heater core in a Volvo 240/740. Volvo guys joke that when they built those cars, they start by putting the heater core on the conveyor belt and then building the rest of the damned car around it. the heater core in MANY vehicles, actually. I can do a 97–01 Jeep Cherokee one in 3–4 hours, but that’s because I’ve got plenty of practice. Most vehicles aside from 80s and earlier domestics, etc have it really buried in the dashboard. A great counterexample is the 91–96 GM B-body sedan/wagon, I can do a heater core or evap core on those in under 30 minutes, not including refrigerant or coolant refill. the rear main seal on an 4.0L powered Jeep is somewhat miserable, but not the worst if you know a couple tricks. pilot bearing, clutch, throwout bearing, all on a manual. Why? Well, they’re located between the engine and transmission, so you are removing one or the other to get at them. Under $100 in parts, hours and hours of labor. similarly, the flexplate or torque converter seal on an automatic. the timing chains (there are 4 of them) on a 4.2L V8 Audi S4 are particularly miserable. Why? Well, they’re on the back of the engine, so you’re spending ten hours to pull the engine, then you have to do 4 timing chains and a bunch of complicated tensioners and guides and put it back in. the alternator bracket oil gasket on a BMW. Yes, that’s a real thing. They put a hole in the side of the engine block because the oil cooler on some models attaches to those ports, but on the particular model I’m talking about, it’s just a bracket that connects the holes together with a 5 dollar gasket that takes a zillion hours to get at and replace. You have to jack the engine up. Don’t buy an E65 chassis BMW X5 unless you’re prepared for some serious pain, folks. the front timing cover on a Ford 6.0L PowerStroke. Why? Well, you have to remove the oil pan, and to do that, I seem to recall you have to remove the transmission, which also means of course removing the transfer case (if 4x4) and the driveshaft(s). Don’t break any bosses off the timing cover or you basically have to gut the drivetrain to replace it… the entire HPOP system, EGR cooler, standpipes, etc on the same 6.0L Ford. Very common issues… and it’s such a pain in the arse to get at that most mechanics literally remove the cab from the truck because IT’S FASTER THAT WAY. Yes, taking half the body off makes engine repairs faster on this truck. Thinking about buying an Expedition or Econoline with this engine in it? I hope you are looking forward to removing literally the entire body from the frame to do engine repairs you can reasonably assume will eventually have to be done, because they all need it eventually. spark plugs and exhaust manifolds on 4.6, 5.4, and 6.8 liter Ford “mod motors”. Some years, the spark plugs break in half when you try to remove them, other years, the replacement plugs strip the holes and fly out when you drive it, denting the hood. timing chains on a 4.0L SOHC V6 Ford. There are 3 or 4 depending on whether it’s got a balance shaft or not. One of them IS ON THE BACK OF THE ENGINE. Why? So Ford could save five bucks by using the same cylinder head casting on both sides of the engine instead of mirror images. What it means? WHEN the timing chain cassette guides fail, you are pulling the engine to replace one of them. fuel tank replacement on a rustbelt Subaru. Why? Well you see, here’s how you do it. First you put the car on the lift. Then you remove both rear wheels, the rear wheel knuckles/bearing housings, the struts (simply because they’re easier to unbolt from the body than it is to unbolt the knuckles from the struts), the rear suspension crossmember and differential, the differential snout T-bar, the rear driveshaft, exhaust… now you can get to the fuel tank. Replace the rear brake pipes and every steel pipe and fitting in the evaporative emissions system while it’s out because they’re all swiss cheese, then put the whole mess back together… and get an alignment done because the whole rear suspension is out of whack now. Oh, they’re steel tanks and rot out in 10–15 years so you have to do this if you live in a state with emissions testing on older cars. Oh and half the bolts I mentioned? They’re either seized solid or screwed into swiss cheese rusty body panels AND seized solid so I hope you’re good with a welder. rear unibody repairs to the subframe that a first-generation Toyota Rav4 rear suspension crossmember mounts to. Especially fun when you don’t want to unbolt any of the parts because you know the whole thing will fall apart if you do, so it’s time to weld the repair panels on without removing the parts that are in your way. The starter motor on a rear wheel drive V8 Toyota pickup or sedan. It’s a fairly cheap part, but guess where it is? Buried in the valley between the two cylinder heads, under the intake manifold and all the parts attached to the top of the engine! The Cadillac Northstar V8 has it in the same place, though it’s a bit easier to replace. rear wheel bearings on the era of Subaru that uses what’s affectionately known as the BAB (“big ass bolt”): If you see this bolt and your rear wheel bearings are rumbling or whining… I hope you’re a decent home mechanic with a 12 ton hydraulic press because otherwise you should pay a pro or sell the car. ANY repair in the engine bay of a W8 engine Passat. Really cool engine? Yes. Really impossible and/or prohibitively expensive to get any parts for it including ones that fail often? Oh yes. Don’t buy these unless you really enjoy the smell of money burning, the glow of check engine lights, and the particularly invigorating feeling of wondering what’s going to break and leave you debating whether to let it sit or spend hundreds on what should be a $5 part. The THERMOSTAT (normally a $2 to $15 part) is $260 to $682. And if it fails you will fail emissions because… the CEL will come on. Why? Because rather than make a solenoid or motor actuated valve and use it to regulate coolant flow… they took a regular thermostat and attached an actuator to it so the computer can move it too. WHEN the actuator fails, the computer notices and on goes the light! UPDATE: holy moly, I didn't expect this answer to be this popular! I think it might be the most-read thing I've ever written and it's only been a day. One of the commenters reminded me of another Awful Repair… clutch hydraulics on a 94-ish Ford ranger. Never again will I work on that mess. Literally everything about it is poorly designed and/or designed with malice and ill intent for every poor bastard of a mechanic who may have to work on it. First of all, it’s what’s known as an “internal slave” type clutch actuator - the slave cylinder is a donut shaped piston concentrically located on the input shaft rather than using a throwout bearing on a clutch fork and a slave cylinder mounted externally to the bellhousing. So if the seals in the slave cylinder go, you have to drop the trans to get at it. The master cylinder is buried under the brake booster, and fed remotely from a little reservoir on the firewall. Normally that’s nice but they mounted it with the ass end uphill and it’s fed from the bottom so it’s proper miserable to bleed - you basically have to bleed it out of the truck, but then you can’t get the freaking thing in without losing all your fluid! Further, they used a particularly hellishly inspired plastic clip to hold the master cylinder pushrod to the pedal - and then buried it as far up into the dashboard as possible… facing the A-pillar… with sheetmetal brackets and junk in the way. And if you lose your temper after screwing with it for 20 minutes trying to unclip it you have to buy a whole new master cylinder because that 5 cent plastic clip is not available ANYWHERE separately (at least for 94-down, I see one for 95-up.) It is presently held on with 3 zipties on my brother’s truck because neither of us felt overly compelled to negotiate with terrorists or pay their blood money. Oh, and the hydraulic line is held into the slave cylinder end with a really miserably designed little quick connect fitting… not the standard one used on trans cooler lines and fuel lines that’s annoying enough, they came up with a whole new miserable design that’s several circles of Hell lower: It seems specifically designed to be impossible to release after 1 day of dirt and salt - the little plastic collar that’s supposed to release those stainless steel barbs gets packed with road dust and the brass corrodes a bit, cementing it in place, and when you try and use the special tool Lisle designed it just mangles the plastic collar and little brass ridge you’re supposed to pry against, and you can only get about 270 degrees of the collar forced down because the bellhousing is in the way of the other 90 degrees! Great design, Ford. Ended up replacing the line along with the slave cylinder. Then the aforementioned bleeding adventure began. It took hours to actually get it right, and reading Ford forums afterward this is not unusual. Protip: just remove the driver side inner fender liner, at least you have room to work inside the wheel well and can bleed the master with it held in a better orientation, hook the line to it, bleed it all, and slap it into the firewall before anything goes wrong. It’s still hell, but at least it’s possible. Suffice to say if I was cursed with such a vehicle repair again I would pay someone else to do it, and I literally do all my own repairs from basic maintenance up to and including AC work, differential R&P setup, trans rebuilds, and electrical fault diagnosis. It would be the first time one of my cars has ever been in a shop for work aside from glass replacement, which I've done but it's actually more economical to have it done than it is to buy the materials myself these days. Those clutch hydraulics are truly an evil, monstrous work by an evil person. These repairs are my least favorite, but I’m sure there are some I’m forgetting and I’m sure there are worse examples.
What was the most difficult car or engine repair or maintenance you have ever done? Were you successful or did you give up in despair?
Generally working on Mercedes. the hardest most physically demanding job i have ever done is the clutch master cylinder on an old 123 series 2 litre mercedes. its located in the drivers footwell, and fed from a remote reservoir. its connected by hard lines to the gearbox, and fitted to a specially engineered bracket….. the problems are as follows. because of the location, i was in the position of having my left side dug into by the sill of the car, with my ribs resting on the top of the sill, while i worked at it from a distance, when i had to get in close i had to lie on the sill in order to get closer to the job….. OUCH. because of its position near the transmission tunnel i was unable to get a spanner on the nuts to remove them from the unit, and because of the construction of the bracket, i was unable to remove the bracket because i could not physically slide it off from the pipe without removing the nuts. after a long time fiddling i had to make a special spanner in order to undo the nuts, so that i could remove the unit…. Then the fun really began…. the unit had to be fitted in the same position, obviously, but i had several problems…. i could not get the pipe for the reservoir onto the cylinder because i could not get my hand down there to do it so i had to remove the pipe and fit it, thread it through the hole and then fish it up…. then i had to locate the cylinder on the end of the pipe at the same time as getting the bolts through it… then getting the nuts on…. luckily i could just barely get my fingertips to touch the nuts, and with the patience and skill of a safecracker was able to thread the nuts on enough to get on my special tool in order to tighten them up enough…. i am a large man, 6 feet 2 tall with a 54 inch chest, believe me this was the hardest and most painful job i have ever done on a car…..ever However….i can add another job….. VW/Skoda……. The front subframe on mk4 golf is in 3 pieces….. the end pieces are aluminium….. set in a pressed steel crossmember…. i think you know where i am going with this……. 5 bolts……. 4 are easy…. no 5 is the bitch it’s an 18mm head high tensile bolt torqued up to 120 foot pounds…… not really a problem…. only its torqued into ALUMINIUM. miracle of miracles… it starts to move… then it binds up….. i snap the head off the bolt. i then commence to try to remove it in the workshop…. its 5 inches long…. threaded all the way with 4 inches inside the aluminium….. so i try all the tricks i can think of…. penetrating oil….. nothing. weld a nut on the end …. nothing. i even get my welder, set it on high and create a short through the bolt….. nothing. i drill it out and helicoil the hole. i get it back in and bolt it up with a new bolt…….. now for the other side…… same shit different day literally….. only this time i just cut the fucking around and chop the head off and go straight to the workshop grind it flat and drill it out. One helicoil later…. its back on with new bushes just like the other side…. coated with a shit ton of ally never seize. and i’m still not happy…. going to source another couple of ends, drill them out and improve them using longer bolts, nuts and washers and make it easier to fix in the future.
Can you replace pistons without removing an engine?
depends on the vehicle. there are plenty of cars that you can r&r pistons with the engine in the car, but sometimes its more efficient to pull the engine and put it on a stand to do the work. the way you chose to do it will depend on your skills and available tools, but ultimately vehicle design will dictate what you can or can’t do. to remove the pistons you need to remove the oil pan to access the rod bolts, then pull off the cylinder heads so you can push the piston and rod up and out of the block. if you cannot remove the heads or oil pan with the engine in situ, then you have to pull the engine no matter what. some cars are definite pulls; cadillacs with northstars, you can barely do anything on those engines without dropping the whole front subframe/engine/trans. subarus, porsches, and other vehicles with flat engines have to come out. crown vics/towncars have a massive frame crossmember running right under the middle of the oil pan, good luck getting that pan out in the car.
Is it possible to convert an automatic transmission Nissan NV 200 to manual transmission?
I’ll start by saying I’m no Nissan specialist… if you were asking about a Toyota, Jeep, Chrysler, Dodge, or Ram RWD/4x4 vehicle I could probably give exact details. So take this as general advise. Yes, it’s possible. Is it financially a wise choice? Possibly, possibly not. What you will want to do is start with a lot of research - is the vehicle available with a manual transmission from the factory? If so, you generally simply need to buy all the components that are different between the two (make sure you’re using the right year donors with the right engine, if there is a difference) option packages you want, remove all the automatic components and bolt on all the manual components. There is a strong likelihood that you will need to have the ECM or PCM reprogrammed to the manual firmware version to avoid going into limp-home mode, having odd driveability issues, and/or failing emissions due to a large number of P07xx series DTCs being set since the automatic transmission no longer exists. Things you would definitely have to change out, on any vehicle, to accomplish this: transmission flywheel, clutch, pressure plate, brake+clutch pedal box assembly, clutch hydraulics, shifter and linkages/cables Things you may or may not have to change out, depending on the manufacturer’s specific design: crank position sensor starter motor CV shafts various transmission and/or engine mounts, brackets, and crossmembers/subframes wiring harness ECM or PCM (if you can’t get it reprogrammed) exhaust components steering column or ignition switch assembly steering/shifter park interlock cable and solenoid This is all assuming the vehicle was available with a manual transmission in the same year as your vehicle with the same engine. If it was not, it gets even more complicated - you have to find a donor vehicle that WAS available with a manual transmission and the same engine (or at least a similar one with the same bellhousing pattern and other specifics) and then do even more research to find where you’re going to get all the other components from and/or how to make them yourself. You may need to find an ECM/PCM programming specialist who caters to enthusiasts doing stuff like this so they can change your ECM/PCM to manual firmware even though such an option was never available factory, which is generally possible but certainly not straightforward. I’ve done it a few times on other vehicles, and my general advise is either to live with the automatic, or buy a vehicle with a manual from the beginning unless you are willing to really get involved in a lot of drivetrain research and then get your hands dirty doing it yourself. My first swap took me weeks of research (and that was on a vehicle that was available from the factory with a manual transmission…) and after having done it four times, I can now get it done in a day, but it’d take weeks again if I chose a new vehicle platform such as the NV200 that I wasn’t intimately familiar with.
What are all of the main parts in an average car and their purposes?
An average car has 30,000 parts. This is probably the most general question I’ve ever seen. Nevertheless, I’ve got a day to spare, so here we go. By the way, your question would best be answered by an automotive engineering textbook. They have up to 8000 pages. Engine: this part provides motive power. In electric cars, this is mostly called the motor. On a gas car the engine will consist of fuel delivery, electrical, cooling, and engine mechanical systems. Electric cars will omit the fuel delivery system, but consist of power delivery, charging, and cooling systems. On steam car there are fuel delivery and combustion systems, steam delivery systems, electrical systems (on steam cars newer than 1910), and lubrication systems. On hydrogen cars there will be electrical systems as in an electric car. There will also be hydrogen storage systems, with extra cooling. In the fuel delivery system, there are pumps, sometimes driven by gears from the camshaft (the part of the engine that drives the valves), sometimes pumped up while driving (on really old cars) like a bicycle pump, but both use diaphragms to create fuel pressure and send it to the engine through fuel lines. These run from the gas tank to the engine, and are usually thin, to keep the pressure high, and metal, for longevity. On old cars, the gas tank was above the engine, and used gravity to flow to the carburetor. On modern cars, the fuel pump resides in the gas tank, and is an electric rotary pump: that means it has an impeller that pumps the gas through the lines. High-powered vehicles need extra fuel, so they have multiple pumps or larger pumps. At the engine there are a multitude of devices that can get the fuel to the cylinders. Diesel cars have always used an injection pump. This serves to distribute the fuel, and also acts on the engine timing. This function is served by gears, belts, or chains in gasoline engines. The injection pump puts a metered amount of fuel into the cylinders, which then ignite the fuel by compressing it. On gasoline or propane-powered vehicles, the fuel is combusted at a lower pressure by a spark plug, which is part of the electrical system. Gas cars initially used carburetors to get gas into the engine. This device takes fuel and combines it with air in a ratio (fuel:air) that is good for combustion. The oldest carburetors are just wicks. Then came single and multi-barrel carburetors. These use a needle jet and a plate to control airflow into a jet of fuel. As cars got fancier, they added more barrels to the carburetors, giving a primary and secondary set of venturis (holes) that could give better response for different engine speeds. The carburetor has been replaced by fuel injection, due to more precise control of fuel leading to better control of emissions and gains in fuel economy and driveability. The first type of fuel injection was mechanical, and was a diesel fuel injection system fitted to a gas car by Mercedes-Benz in the 1950s. Also in the 1950s, the first electronic fuel injection system was attempted by Chrysler, but proved unreliable. Fuel injection, when it started again in the late 1970s, had a single injector putting fuel into all of the cylinders. This was called single-point or throttle-body fuel injection. Most implementations of this use the carburetor body with a fuel injector inside. Multi-point injection put injectors on all of the cylinders, providing still better control of fuel. These need a fuel rail, where fuel is pumped at high pressure to the injectors. Injectors put a spray of fuel into the cylinder, where it combines with the air, and is then combusted. On a steam car, fuel is used only for the boiler, which generates steam to drive the car. It is combusted in the boiler, which consists of a series of tubes that heat and pressurize the water to make it useful for powering the pistons. Now for the air: Air comes into the engine through an intake manifold and an air filter. The first cars did not have a filter or a manifold, and just took air in through the carburetor. As time went on, manifolds were added. The carburetor mounts to the manifold and the air cleaner mounts to the carburetor. Older air cleaners would make air travel through a pool of oil before it went to the carburetor. This trapped dirt in the oil. Newer filters use a folded paper filter with silicone or rubber seals to trap dirt and debris. As fuel injection became common and it was more desirable to have better computer control over combustion, the air filter was moved to a separated air box. This has a mass airflow sensor, mass air pressure sensor, or both, attached along the intake pipe. A turbocharger or supercharger will also have a connection to the intake pipe. Once the air has mixed with fuel and combusted in the cylinders, it is exhausted out of the engine. The exhaust started as a straight pipe, but as the car evolved in the 1910s, mufflers were added to quiet the loud exhaust. In addition, the mufflers (which have many metal baffles inside) served to condense some of the gases from the engine. Attention paid to emissions, starting in the 1940s, resulted in catalytic converters being fitted in the 1960s and 1970s. These utilize metals which can combine with some combustion byproducts, lowering harmful emissions out the exhaust (tailpipe if it comes out of the rear of the car, sidepipe if it comes out the side, and exhaust stacks if it comes out the top). There are typically 2 of these, one mounted close to the engine, and one further along. They will have sensors to indicate proper functioning to the engine computer. Turbochargers and superchargers are both means to increase the amount of air that comes into the engine, to increase the amount of power that can be produced from one combustion cycle. These employ various forms of air pumps to provide extra air for combustion. Superchargers are driven by belt, gears, or transmission from the engine and turbochargers are driven by exhaust gas pressure. Both have a connection to the air intake. The roots blower is the oldest form of supercharger. It utilizes two lobed gears that mesh with each other to pressurize the air. The screw-type supercharger uses screws that mesh together to accomplish the same thing. The Powerplus and scroll-type superchargers use rotating forms on eccentrics (the Powerplus has plus-shaped rotors, and the scroll-type has spiral-shaped rotors). These rotating forms are more compact than screw or Roots-type superchargers. Turbochargers use a turbine connected to the exhaust to spin a turbine connected to the intake. These turbines are connected together in one housing to form the turbocharger unit. The turbines are mounted to a central shaft that has bearings capable of withstanding the turbines’ high speeds. The electrical system for gas cars consists of the battery, alternator or generator or magneto, ignition system, starter, wiring, and engine electronics. The battery stores the energy from the magneto (direct current), generator (direct current), or alternator (alternating current). These all rotate a coil of wire (the armature) through a magnetic field (the stator). The magneto uses permanent magnets and the dynamo/generator and alternator use electromagnets. A commutator on magnetos and dynamos or generators switches the contacts the windings are using to produce a constant pulsed direct current. Alternators do not need a commutator. Brushes (made of carbon) are used on older magnetos or dynamos. The oldest cars just have a heated tube to ignite the fuel mixture, moving on to coils that magnetos or dynamos and spark plugs. The first cars, having only a single cylinder, did not need to power more than one spark plug, but soon, 2 and more cylinders came along, which required a distributor. This has an ignition coil that transforms the 12 volts created by the magneto/generator/alternator to 15–30,000 volts. That is then transmitted to the rotor, which turns to contact several points. This is driven by gears from the engine camshaft. The points are contact patches that send the power to the spark plug wires and then the spark plugs. This is called inductive discharge ignition, due to the current being induced in a coil and sent to the plugs. In the 1980s, individual coils started to be used, phasing out the rotor, and the electronic triggering of those coils that started in the 1950s continued to be applied. The coils have moved to being mounted on the spark plugs on modern cars. There are also capacitive discharge ignition systems that use a capacitor to supply the current to the spark plug. As the engine speeds up it needs to have the spark appear sooner, so the timing is advanced by a governor attached to the distributor shaft. That moves the contacts ahead, so that the spark occurs sooner in the combustion cycle. That is the mechanical spark advance, though the earliest cars with spark plugs would often have the driver move a lever on the steering wheel that connected to the contacts, accomplishing the same thing. There is a vacuum spark advance as well, which uses the air pressure from the engine’s air intake to move the contacts. The spark plugs that the coils fire consist of a ceramically-insulated electrode, a threaded shell to attach to the engine, and a spark gap on the end of the plug that will be inside the engine, created from the shell that is insulated from the electrode. The other end of the electrode is called the terminal, and connects to the spark plug wire. The ignition system isn’t the only direction that power flows, however. There are lights, heaters, computers, wipers, switches, and gauges to be powered. These all go through a fuse box, and sometimes through another fuse box (1 for the engine, 1 for the interior). The fuse boxes can also contain relays, which are heavy-duty switches, and are often not as easily replaced as the fuses. The fuse prevents electrical damage by burning out if the current becomes too strong. Car lights started as gas-fired lamps in front, which used acetylene gas (created from dripping water onto calcium carbide) burned for light. These could explode energetically if too much gas was produced, and didn’t provide strong light, needing reflectors to direct the light. They were gradually replaced by electric lamps from 1908 on, and by the 1920s electric lighting was the norm. Electric light bulbs pass current through a tungsten filament, which creates heat and light. Low beam headlights will put the filaments higher in the lamp, which results in a light pattern lower on the ground. High beam headlights put out a stronger beam further out. Bulbs were replaced by sealed-beam headlights in the late 1930s. This puts the reflector and elements into one sealed unit. Later, headlights moved back to using separate bulbs and reflectors. High-intensity discharge headlights use an electric arc between electrodes to produce light, while LED headlights use a semiconducting crystal that emits light when current is passed across it. Taillamps started to come into use in the 1910s. Trafficators allowed drivers to indicate their desired direction of travel, but were not electric, being a metal flag that could be lowered from one side or the other of the vehicle. Due to their inconspicuous nature, electric light turn signals were soon added. These lights pass a current through a bi-metallic strip, which heats up as current passes through, and eventually breaks contact. It cools, and then makes contact again, causing (on earlier cars) the ticking noise that often accompanies turn signals. Cornering lights are a 1970s addition, and fog lights (front and rear) are a 1950s addition. Reverse lights started coming in in the 1970s. High-mounted stop lamps became mandatory in North America in the mid-1980s. Side marker lights have been mandatory in North America and Europe since the 1970s. Since the 1970s, brake lights/taillights, turn signals, and side marker lamps have all incorporated retroreflectors to increase their visibility, even when the light is off. These all serve to make the vehicle more visible to other drivers or make the driver more aware of their surroundings. Spotlights are an accessory that allow the driver to shine an external lamp or lamps where they would like. The car’s heater is a part of the cooling system, these days, but was a part of the air intake in the past. It consists of a blower fan that draws air in from the engine bay and distributes it to the passenger cabin. Older cars merely use the heat on the top of the engine spread directly to the cabin. Cars from the 1930s on have a separate heater core that takes heat from the radiator through hoses, and mixes in air from outside (usually vents at the base of the windshield), controlled by a door that can limit airflow to the heater core. Cars can also have an air conditioner, which compresses a refrigerant, then gets cool air from the expansion of that refrigerant. This is combined with the heater to make up the HVAC (heating, ventilation, and air conditioning) system. The air is blown into the car, sometimes through a filter, through a series of vents. There are usually vents in the cowl (the top part of the dashboard) to defrost the windshield, and vents in the top and bottom of the dash. Some cars also have vents to the rear of the car through the roof or under the floor. These vents are connected to the fan by ducts. Computers are omnipresent in cars these days, controlling the cars electrical and fuel systems. These are frequently mounted in the engine bay in a sealed module, often put close to the engine fuse box. The common computers are the engine control unit (ECU), body control unit (BCU), and transmission control unit (TCU). The transmission control unit is sometimes integrated into the ECU. Computers are switches, at their most basic level. The wiper motor is mounted in the top of the engine bay, and moves up to 3 rubber strips across the windshield to clear rain or dust. It consists of the electric motor for the wipers (early cars used vacuum for this, but it was not as good a solution, since the amount of vacuum an engine produces decreases under load), a gear rack and limit switch, the wiper linkage, and the wiper arms and detachable blades. The gear rack changes the electric motor’s rotating force into linear force. The limit switch changes the direction of the wiper motor. The wiper linkage connects the gear rack to the arms and the wiper arms connect to the linkage and the wipers. The wipers do the actual work on the windshield. The switches send power different directions. There are usually springs to make the switches click. Gauges were mechanically-moved for much of their existence, but during the 1970s tiny electric stepper motors and electronic controls started to replace the mechanical parts. The newest cars have displays as gauges. Radios are an automotive accessory that have become part of a car’s standard equipment over the last 40 years. They are sometimes called the “head unit”. They take radio waves and change them into electrical signals. These signals are then sent to an amplifier, which makes them more powerful, and then to speakers, which change the electrical signals to sound waves by vibrating a diaphragm, with the use of a wire coil, called the speaker or voice coil, and an electromagnet. The amplifier uses a switch called the crossover to send the signals to the appropriate speaker. Tweeters are small, fast-moving diaphragms that reproduce high sounds (2000–20,000Hz or cycles per second). Mid-range speakers are larger, putting out sounds between 250 and 2000Hz. Woofers are large, slow-moving diaphragms for lower sounds (50–1000Hz), and subwoofers are really large, slower-moving diaphragms for very low (20–200Hz or cycles per second) sound waves. Full-range speakers do their best to reproduce all of those sounds. The radio decodes the strength of the signal (AM or Amplitude Modulation) or the frequency of the signal (Frequency Modulation or FM) to deliver the electrical signal to the amplifier, crossover, and speakers. Radios that incorporated record players were optional for a short time in the late 1950s and early 1960s. Record players read grooves in a vinyl (in this case) platter with a stylus. They are very sensitive to vibration, so low frequencies can sometimes push the stylus out of it’s groove, causing the record to “skip” a groove. Road vibration also would have caused records to skip, despite efforts to isolate the player from the road. The next addition to radios came in the form of tape players. These cassette players read magnetic tape stored on a reel (or reels) in a cartridge or cassette. The tape is then moved past a transducer (called a read head) that can read one or two tracks of magnetic information from the tape, which is then converted to electrical information for the head unit. Citizen’s Band transmitter-receivers (transcievers) were a popular option in the 1970s into the early 1980s. Cassette players (and earlier 8-track players) were joined and then replaced by CD players starting in the 1980s. CD (Compact Disc) players read the bumps and flat surfaces (pits and lands) on a spiral track embedded in a disc. The disc is spun at a constant velocity by a motor, and read by a laser. The digital information produced by the laser is decoded and turned into electrical information by a DAC (digital-to-analog converter). That electrical information is sent to the head unit. Recently, other digital forms of information have come to be used as radio accessories, such as MP3 files (the digital information, as on a CD, but compressed) stored on hard drives (magnetic platters spun past a transducer that can read the information, or silicon chips that store the information without a motor), or USB sticks (Universal Serial Bus) that do the same as hard drives. Bluetooth connection to phones is becoming more common these days, too. That is a wireless communication standard using high-frequency radio waves, picked up by an antenna connected to the car’s entertainment system, which has gained the term infotainment system as more controls for the car, such as the HVAC controls and other comfort and mechanical settings, were incorporated into it. The cooling system of the engine makes sure that the engine remains at a good operating temperature. The coolant (water and glycol) is circulated through the engine by a water pump, which uses a rotary impeller driven by an electric motor or by a pulley attached to a drive belt. This goes through passages in the engine and hoses to a radiator, which spreads and dissipates the heat through many tubes and delicate fins. Radiators are typically aluminum (aluminium) for light weight. The engine coolant also circulates through hoses to the heater core. There is a fan to push air through the radiator, and sometimes there are two. The oldest cars used thermosiphon cooling, where hot water would circulate cold water through the engine. This worked for lower-speed engines, but not for higher-speed engines, so they added a fan. Older cars (1900s to 1930s) connected the fan directly to the crankshaft of the engine. Newer cars (1920s to 1970s) used a clutch to engage and disengage the fan, which reduced power losses from drag. Even newer cars (1980s to today) use fans powered by electric motors. Thermostats are switches that allow water to flow. Some are electronically controlled, but the most common have a wax pellet that melts at a certain temperature, to allow a valve to open and coolant to flow. Some cars use an additional radiator for the transmission, called a transmission cooler, to keep the transmission oil cool. This radiator doesn’t circulate coolant, but instead circulates the transmission oil. Some turbocharged cars use a radiator to cool the air coming into the engine. This is called an intercooler. Intercoolers use outside air to cool the air that has been compressed by the turbocharger, making it denser, and allowing more complete combustion. Electric cars send coolant to the motor, and sometimes circulate it through the battery pack. The mechanical parts of an engine do the work of driving the engine along. The engine in most cars is separated into the block and the head. The block is the bottom of the engine, where the crankshaft is located. The crankshaft converts the linear motion of the pistons into rotation. Turbine-powered cars just have a driveshaft, and use the compression of fuel to combust it and turn the turbine. The Wankel engine’s driveshaft converts the eccentric motion of the rotor to rotation. The crankshaft is connected to the pistons by connecting rods, which attach to the crankshaft with a bolt-on rod cap, and to the piston with a wrist pin. There is a bearing sandwiched between the rod cap and the rod that allows it to move freely around on the crankshaft. The crankshaft attaches to a flywheel at the back of the engine, which stores some kinetic energy and serves as a connection to the transmission. The front end of the crankshaft connects to the fan, drive belt pulley, and main drive gear, which drives the camshaft in almost all cars, and in cars with a geartrain, the water pump, oil pump, fuel pump, and electrical generator or alternator. The head is attached to the block with a head gasket (or, on engines with more than one bank of cylinders, head gaskets). This seals the two parts together, and makes sure that the coolant, oil, and fuel stay separated. The block or the head can contain the camshaft, which drives the valves and is usually driven from the crankshaft. The valves allow air and fuel in (intake) and let exhaust out. They are spring-loaded plates that cover holes in the head. The springs push the valves open. Early cars drove only one valve, the intake valve, and let exhaust pressure open the exhaust valve. Eventually they drove both valves off of the camshaft. In overhead valve engines and flathead engines the valves are moved through pushrods. The camshaft pushes on the pushrods, the pushrods push on tappets, and the valves open. In overhead cam and dual overhead cam setups, the crankshaft drives the camshafts through toothed belts or chains, and the camshafts push on the valves through rocker arms. Newer cars add a roller to the part of the rocker arm that contacts the camshaft, called a roller finger follower. There are exceptions to valves: sleeve-valve engines use the crankshaft to rotate two sets of sleeves with holes in them that act as the valves. Two stroke engines draw air and fuel into the combustion chamber with reed valves (older cars) or just with ports (loop-scavenging later cars) and Detroit Diesel engines use a supercharger to bring air to the cylinder. The FreeValve system doesn’t use cams at all, but sends signals to electromagnetic actuators to move the valves, and the Fiat MultiAir and Jaguar Ingenium systems use hydraulic actuators. The whole assembly is lubricated by oil. In early cars a system called total loss lubrication was used. The engine would be mounted flat, and the whole assembly would sit in an oil bath. Oil would be flung about by the motion of the piston, and most of it would wind up being burned. Splash lubrication was a refinement that kept the oil in the sump and splashed it around, through holes drilled for that purpose. It was limited to low-speed use, though, so pressure lubrication was added to engines in the 1920s. This added an oil pump, usually a lobed pump, like the Roots blower, or a gear pump. An oil filter was added in the 1950s to prevent engine damage from debris in the oil. The oil pump provides hydraulic pressure to variable valve timing systems, as well as lubricating oil. Engines with pressure lubrication soon had oil passages to go with their already existing cooling passages. Now, for the other bits. The driveline and body bits. Driveline refers to the system that transmits engine power to the road. The transmission, driveshafts, joints, wheels, and tires are part of this system. The bodywork is the external and internal structure that holds everything together. The Transmission is a set of gears that multiplies the torque (twisting force) of the engine to the wheels by changing the speed at the output shaft. Transmissions get power on their input shafts and transmit power out on the output shaft. Manual transmissions and some automatic transmissions use a clutch, which is a mechanical coupling that connects and disconnects the transmission. Clutches consist of a disc that is sandwiched between the flywheel and a pressure plate. The engine drives one of the plates, and the transmission is connected to the other plate. The plates are pulled apart by a lever actuated by the clutch pedal inside the car. The lever pulls on a plate, called the pressure plate, that has springs to smoothly disengage the clutch. When the plates are apart, the flywheel spins independently of the transmission, but when they are together, they rotate as a unit. Manual transmissions use a lever to select a set of gears, which is then engaged with the clutch. There is a position in all transmissions where no gear is selected, called Neutral. Automated manual transmissions operate the clutch with a motor, as do preselector transmissions. In a preselector gearbox, only the first gear is engaged by the driver, and every forward gear after that is selected inside the car, then shifted to by the transmission. Alternatively, some used a fluid-filled torque converter. Torque converters are mostly used by automatic transmissions, though some have been used behind manual transmissions as well. They consist of two turbines, one driven by the engine, and one driving the transmission. This can convert the torque of the engine like a transmission itself, multiplying it through different stages. Automatic transmissions use hydraulic fluid to engage different sets of epicyclic gears, through the use of hydraulic pressure on control valves. Newer automatic transmissions use the TCU or ECU to control when the transmission shifts. Paddles on the back of the steering wheel can also be used to manually control an automatic transmission. CVTs (Continuously Variable Transmissions) are a type of automatic transmission that uses pulleys that can change their effective diameter by changing the space between their cone-shaped halves. A steel (on early cars, rubber) belt connects the two pulleys. Early CVTs were controlled by a weighted governor forcing the pulleys together with the aid of a ramp, but most modern automobile CVT pulleys are driven together or apart by hydraulic pressure. Transmissions are mounted to the body of the car or a frame crossmember by rubber or oil-filled hydraulic rubber mounts that dampen vibration and torque reaction. The transmission drives a driveshaft or a pair of driveshafts, in the case of front wheel drive cars, or both, in the case of four or all-wheel-drive cars. Front wheel cars, and some rear wheel drive cars, combine the differential (a special gear train that splits power between two wheels) and the transmission to make a transaxle. The transaxle drives the wheels through two constant velocity joints (CV joints). The oldest cars used chain drive, without a differential. Older cars used universal joints to drive the wheels, because the wheels don’t just rotate, but travel up and down on the suspension. Universal joints were soon replaced by Rzeppa-type CV joints, however, due to the increased smoothness of that design. Rzeppa-type CV joints use an inner and outer shell, and ball-bearings in a cage between the two, transmitting the power between them. The driveshafts attach via the CVs to the axles. The axles in turn attach to the wheels through the hub, which rides on a wheel bearing attached to the suspension. On rear-wheel drive cars, or four-wheel drive cars, the driveshaft attaches to the output shaft of the transmission and attaches to the rear differential. Some use a torque tube, which is a driveshaft inside a tube, for better protection from the elements, and a more solid frame to transmission connection. Some four-wheel drive cars have a center and front differential as well. The driveshaft connects through two universal joints to the rear differential. The differential uses an epicyclic (planetary) gearset with two pinion gears to send power to the rear wheels. If one wheel loses traction, the differential sends power to it. This is known as an open differential. A limited slip differential limits how much slip one wheel can have. It uses clutches or gears to control how much any one wheel can slip. Axles that do not have driven wheels are called solid axles, and axles with differentials and driveshafts are live axles. Some cars use leaf springs as axles. Hotchkiss drive cars connect the axle directly to the leaf springs through shackles. The suspension cushions against road impacts. There are two main types of suspension: air suspension, and springs. Leaf springs are the oldest type of spring, and consist of curved metal leaves, attached to the car by shackles. Elliptical springs form an ellipse, while semi-elliptical springs are more common, and are half of an ellipse, Leaf springs attached underneath the axle are called underslung. The springs attach to the frame, subframe, or body of the car. Coil springs typically sit in cups at both ends. They take up less space horizontally than leaf springs, but more space vertically. Coil springs with telescopic hydraulic shock absorbers inside are called struts. MacPherson struts are the most common design that uses this arrangement. A carrier attaches the strut to the axle. Lower control arms attach to the bearing carrier on the wheel, or to the axle. The carrier attaches at the top to a radius rod. Chapman struts use the driveshaft as the control arm, and angle the strut on top to act as a control arm. Independent suspension allows one wheel to move independently of the other. Most cars have independent front suspension, but dependent rear suspension attached to a solid axle. Most dependent rear suspensions have a Panhard rod (track rod) to locate the rear axle laterally, and multiple links to the body to locate it along the body. Double wishbone suspension uses a spring and suspension connection to the body, and a set of control arms attached to the wheel bearing carrier. They most often use coil springs. There is a third type of spring, the torsion bar. This uses a bar that is connected to the suspension arm as a spring. Deflection of the arm twists the bar. It is popular to use torsion beams as rear suspension in cars and minivans. Air suspension uses bags of air to support and cushion the car. It is sometimes used to supplement spring suspension. Shock absorbers were initially just discs that could be tightened to dampen spring motion, attached to the axle and body by two lever arms. Hydraulic direct acting lever arm shock absorbers were next, they dampened the rotary motion of the arm with vanes inside an oil-filled drum. Tubular telescopic hydraulic shock absorbers started seeing use in the 1960s. Oil was forced through holes in a piston, which was allowed to telescope and contract. These are in use today, though some incorporate air fittings to be used as inexpensive alternatives to the airbags in air suspension. Citroën uses a hydropneumatic suspension, which uses air-filled spheres which allow oil to flow freely under pressure between the spheres to level the suspension automatically. The hydraulic fuel in the spheres is sent to the steering to assist it as well. Steering on a car is accomplished in two main ways: through a rack and pinion gear or recirculating ball. Rack and pinion is very simple, consisting of just a rack of gears, and a pinion gear, but it must be mounted fairly low in a vehicle. The rack acts directly on the linkage attached to the wheels. Recirculating ball steering circulates ball bearings through a worm gear enclosed in a block. Teeth on the outside of the block engage a Pitman arm, which engages the wheels through steering linkages. As for brakes, early cars didn’t have much of them. Early brakes used levers to push a block against the wheel, and parking brakes pushed a block against the driveshaft. Drum brakes came later, and use a hydraulic piston to push two pads (called shoes) lined with friction material out onto a drum. The shoes are often engaged by levers to ensure even braking force. Disc brakes clamp a disc (the rotor) between two pads. The frame that carries the pads is called the caliper. There can be more than one piston in a brake caliper. Initially cars actuated brakes by means of rods, but during the 1920s brakes switched to hydraulic actuation. Power assistance for brakes came from vacuum brake boosters in the 1930s, and from a power brake pump in the engine bay from the 1950s on, accompanied in the 1980s by hydraulic assists to the clutch. Power assists for steering also came in the 1950s, with their own separate pump. Modern cars use computers, in conjunction with cameras, to provide several steering and brake-related safety features. Collision detection features use ultrasonic sensors in the front bumper or radar to detect objects in front of the car. Lane-keeping assist can activate the steering to keep you in your lane if the camera on the car sees that you’re straying from your lane. Seatbelt pretensioners take the slack out of seatbelts in the milliseconds before a crash. Airbags use ignitors to inflate in a fraction of a second, protecting occupants from coming into contact with the body of the car. A note on wheels, which have gone from wooden “artillery-style” wheels with clamp on tires, to stamped steel discs with safety bead rim design, to lighweight aluminum wheels, with a stop by magnesium wheels in the 1960s and 70s. Tires have gone from solid rubber to balloon tires, bias-ply to radial, with the reinforcing steel or nylon bands traveling in the direction of the tread with bias-ply, and across the tread in addition to with the direction of the tread with radial. The body consists of doors and windows. Cars used to be made on a frame, with several crossmembers, and the body would sit on top. The only vehicles that are mass-produced this way today are pickup trucks. Car bodies started out as carriages, and like carriages, they were made of wood. Metal bodies debuted in the 1910s, and leather tops gave way to hardtops or enclosed cars like sedans, coupés, and limousines. Unibody cars were first introduced in the 1920s by Lancia, an Italian car company. They combined the frame and the body into a single unit. They were taken up by most companies by the 1960s, with a resurgence in popularity in the 1990s. Today, only trucks and a few SUVs are built on separate frames. The 1940s brought a new body style to the fore, the station wagon, called an estate car in some countries. This utilized the sedan’s basic shape, to the back window, but added a cargo area by continuing the roof to the tail of the vehicle. Early station wagons had wooden sides, quickly becoming wood paneling, and then wooden applique in the 1960s. Convertibles using power-assisted tops became common in the 1940s, and soon after, power windows became an option. The first folding power hardtop convertible came out in 1958, utilizing many limit switches and motors. Power mirrors were added to the power option list in the 1960s, with power seats coming next. A few cars used hydraulics to power seats and windows, but after a short period where cars used vacuum power, almost all cars switched to electric-powered windows and doors. Heated seats and mirrors started to become an option during the 1980s. Plastics made their first appearance in the 1920s, and spread far and wide in the 1950s, becoming an unavoidable part of every car in the 1990s. The seats in a car are mounted to the floor by seat rails. The lower seat cushion (squab to some) is sometimes manually adjustable. Modern cars have ventilation in the seats, allowing cooling as well as heating. Luxury cars have massagers in the seats, too. Initially, all cars had bench seats, though a few luxury cars added jump seats to the back to expand passenger capacity in a pinch. These folded down from the front seatback. Bucket seats came with the first sporty car, followed by the first folding seats, rumble seats, that disappeared into the body when you didn’t need them. On the safety front, seatbelts were developed in the late 1950s, and retrofitted sporadically to cars, before becoming mandatory in North America in the 1960s. Side door guard beams and crumple zones were added during the 1990s. Roof crush tests have led to reinforced roofs. Even the glass roof of a Tesla can withstand the weight of the car. So, there you go, an extremely rough overview of everything in a car.
Beranda