As batteries age and distribute and receive recharges, they get white hair just as we do, in the form of a powder that will appear on the top. Once the battery is disconnected properly this can be cleaned up harmlessly, but eventually, like all batteries, it will have to be replaced when it fails to perform.
OIL
You probably know a lot about this system already. Oil helps lubricate and clean all the different metal parts that would otherwise grind against one another in the engine, destroying your car. It’s stored in the oil pan when the car is turned off; when the car is running, it’s pumped around the moving parts of the engine by an oil pump, lubricating as it goes. An oil filter cleans out the sludge and particles. A dipstick lets you check how much oil you have (as well as its quality), and an oil filler nearby lets you add more when it’s low—or refill completely when you’re changing the oil.
Reading a Can or Bottle of Oil
We’ll say this again later when we talk about checking, filling, and changing your oil, but we’ll say it now just to make sure it’s burned into your head: Only buy the kind of oil recommended in your vehicle’s owner’s manual.
Like any other liquid, oil is thinner when hot and thicker when cold (on its way to freezing). This texture or ease of flow is known as viscosity; high viscosity means thick and sludgy, and low means thin and watery. Oil needs to remain thin enough when cold to flow and lubricate everything completely when starting and thick enough to “stick” to the parts it’s lubricating when hot.
Most oil you buy is multiviscosity, so that you don’t have to switch types at different times of the year. The numbers on a can that say something like 20W-50 indicate the range; the higher the number (50) the higher the viscosity, the lower the number (20), the lower the viscosity. The letter W after a number, usually on the lower end of the range, indicates that the oil has been winter tested.
The quality of oil for a gas-powered car begins with an S and is followed by a letter, with A being the lowest. If you have a new car, your manual will probably recommend SL or SJ. Higher quality oils can always be used for cars whose manuals suggest lower quality oils; the reverse, however, is not true. In fact, SA through SH are considered obsolete now—it’s best just to never use them.
Oil is not the place to begin penny-pinching with your car; always make sure it’s a quality brand that has been certified by the American Petroleum Institute and says “Energy Conserving.”
(If you drive under tough conditions—towing a trailer, navigating hilly areas, or just high-speed driving—you may want to consider the added performance of synthetic oil. Synthetics cost more but can help extend the life of your engine.)
HEATING/COOLING
For Your Car
If you hadn’t already figured it out by now, with all those explosions going on in your engine, the bigger issue is cooling rather than heating. Temperatures can reach over a thousand degrees under the hood, and if left unchecked things could start to melt. To keep this from happening, your car’s engine is equipped with a liquid cooling system (unless it’s equipped with an air-cooled engine).
Coolant is stored primarily in the radiator. When the engine is running, a pump runs the coolant into a hose at the bottom of the radiator and through the water jacket around the engine, where the liquid picks up heat. Coolant is then carried back to the radiator via a hose in its top. The radiator in your car works similarly to one you might find in a house: It helps radiate the heat off and out of the coolant and into the air (in front of the grille), with the help of a fan when the car isn’t moving to flow air across the fins of the radiator to remove the heat. The now cooled-down coolant gets pumped back into the engine, and the process starts all over again.
There will often be a coolant reservoir next to the radiator; if there is, you add coolant there instead of directly into the radiator. When coolant heats up it expands (as do most liquids), and the reservoir catches the extra when it overflows the system to keep it from leaking all over the ground. Leaked coolant is actually more of a hazard than a lot of the other toxic chemicals that could leak out of your car.
Coolant is usually a mixture of water and antifreeze; this fluid has a higher boiling point than water and a lower freezing point. The antifreeze is usually ethylene glycol. Ethylene glycol tastes sweet and is deadly poisonous. Dogs love it. Small children love it. Even a tablespoonful can be fatal. So be very careful where you keep extra and when you refill the reservoir or radiator—clean any spills immediately.
For You
Heating is easy! Heat from the engine is carried via the heated coolant to a small radiator behind the dashboard, and just like the engine radiator this one dissipates heat and a fan distributes it through the appropriate vents.
Air-Conditioning
Cooling is … not so easy. Basically, a liquid called a refrigerant is pushed through an evaporator, where it absorbs and removes heat from inside the car. It does this because it has a very low boiling point (meaning it boils at a lower temperature than plain water), and when a liquid turns into a gas it picks up heat. From there it gets sucked into a compressor—taking the heat with it—where it’s compressed, then fed down a radiator-like device called a condenser. This is generally located in front of your engine coolant radiator. There the gas condenses, turning back into a liquid (think of the water droplets that form on the inside of a glass kettle after the water stops boiling and cools down), releasing the heat through the car’s radiator. From there this high-pressure liquid is fed through a small orifice called an expansion valve (or orifice tube) and converted back to a low-pressure liquid, then sent onward to the evaporator again.
This process is complicated—you’ll notice we didn’t bother to include any of the words in the glossary—and the whole system is best left to a technician if anything goes wrong.
FUEL
Diesel! Ethanol! Methanol! Fuel cells! Leaded! Unleaded!
Aaaaaaah! Relax. We’re going to deal with “normal” unleaded gas, the kind you usually get at the pump. There are only three things you really need to know about it.
First of all, gas isn’t just gas; it’s usually gas plus detergents, which help keep your engine clean.
Second, gas “quality” is measured in octane. The octane rating indicates how likely the gas is to explode badly in the cylinders, misfiring and causing what is technically known as a spark “knock” or a “ping.” Gas with a higher octane burns completely and more smoothly; gas with a lower octane burns faster (and less smoothly). Check your owner’s manual for the octane that’s best suited to your engine; use anything lower and you could be damaging the engine, and use anything higher and you’re probably wasting money on something you don’t need.
And third, your car doesn’t run on gas. It runs on a mixture of gas and oxygen; in fact, most of the explosion that moves the pistons is air!
And here is how it all works.
The fuel pump in your car—either mechanical (driven by the engine) or electrical (powered by the battery and alternator)—brings the gas from the tank to the engine through the fuel filter. Air comes into the engine via an air inlet hose or snorkel or through a filter.
In the days of carburetors, the throttle plate hooked to your gas pedal would determine the amount of air and fuel going into the engine, and the throttle would determine the ratio of gas to air when you pressed down on the accelerator. Today all cars have electronic fuel systems with computers and injectors, which decide how potent a cocktail of gas and air gets injected into the cylinders. In this case, consider air the alcohol and gas the mixer; the more air, the bigger the kick!
You should always keep your tank at least a quarter full; even with a filter, crud and grit collects at the bottom of the tank—and you really don’t want that going through your engine. Also, keep track of your mileage and compare it to what the manual says your car should get; if you’re consistently less than normal that means there could be a problem.
TRANSMISSION/DRIVETRAIN
As with many things in life, you can only have one of two things at any given time in a car: power (torque) or speed.
Welcome back to our bike metaphor! In almost exactly the same way you shift gears on your bike to generate more power or speed, your car needs to shift gears to do the same thing.
Imagine the gears on the bike moving. You can see that for every single rotation of the big gear, the smaller turns many more times—and at a faster rate than the big gear does. The same is true for a car; in high gear the wheels turn several times for every single rotation of the larger “engine” gear—which means they turn a lot faster. Because you have speed, you don’t have power, which is why you’re in high gear during highway driving but not when you’re going uphill, starting up, or pulling a heavy load.
In low gear, the wheel gear only turns once for every several turns of the engine gear (about 2.5 to 1); the engine gear turns faster and the wheel gear slower. That means more power to the wheels. This is why you use it to go up steep hills or to start the car moving, but not to travel at high speed.
(Actually, in cars at low gear the wheel and engine gears are approximately the same size, so the car goes slowly with the full power of the engine.)
The “gear box” in a car is called a transmission.
Because there’s no “chain” in a car and the crankshaft is connected more or less directly to the transmission, the engine has to disengage itself physically from the gears so the engine does not stall when stopped. You do this with the clutch in a manual transmission; the car does it for you in an automatic transmission, using a torque converter.
Out the other side of the transmission, the crankshaft is now called a driveshaft. It leads to the differential in a rear-wheel-drive car, which turns the rotation of the shaft ninety degrees to move the wheels forward. The differential also determines the individual speed of each wheel when you turn: The inside wheel turns slower, the outer wheel faster.
In front-wheel-drive vehicles, the differential and the transmission are combined into the transaxle.
STEERING/SUSPENSION
Repairs and service to the system are generally known as front end work, since the rear wheels don’t do any steering on most cars. Your steering wheel is connected to a steering column that probably controls a rack-and-pinion steering system. The wheels are connected to the car at the steering linkage by means of ball joints, which allow a freedom of movement to the wheels, just as your upper arm does in your shoulder socket.
The suspension system keeps your car from flying up into the air every time you hit a bump. Springs suspend the vehicle and let the wheels maintain contact with the ground at (almost) all times, expanding if there’s a pothole and compressing if there’s a bump. But springs don’t just expand and contract in one smooth motion—picture taking a big jump on an old spring bed. It keeps bouncing for a while long after you stop; in a car, this would keep you happily carsick for the entire length of the journey. Shock absorbers smooth out and slow down the rest of the bounces, just as the cylinder on a storm door keeps it from slamming shut.
There are two basic kinds of suspension. The double wishbone has a pair of control arms that cradle the wheel at their wide end and the spring and shock absorber at the narrow end where they come together.
A MacPherson strut is more like a vertical rod and acts as both the spring part of the suspension and as a shock absorber.
BRAKES
There are two different kinds of brakes—drum and disc—but both operate on the same two basic principles; friction, and the fact that liquids don’t compress. Think of a sealed juice box: When you squeeze it, does the box get smaller as it forces the liquid into itself, or does it explode juice out the top and all over you?
Putting your foot down on the brake forces brake fluid out of a hydraulic master cylinder. The fluid then goes into the brake lines and up to the brake cylinders that operate the brakes.
With disc brakes we can go right back to our bike metaphor. Just like the pair of calipers that squeeze against your bike tire to make it stop, there is a pair of calipers that squeeze the brake pads or friction material against the rotor, or disc, which is directly connected to the wheel. When you press the brake pedal, brake fluid is forced into pistons in the calipers. Because the fluid doesn’t compress, it has no place to go, so it pushes harder and further against the pistons. This forces them out to make the pad press against the rotor. Friction causes the rotor, and therefore the wheel, to stop.
With drum brakes, instead of a disc directly connected to the wheel, there is a metal—you guessed it—drum. Inside the drum are a pair of brake shoes with a wheel cylinder between the two shoes, containing pistons, which are forced outward in the cylinder when brake fluid is forced into it (remember the whole liquids-not-compressing thing?). The pistons push out against the shoes (which are lined with the same material as disc brake pads), which in turn push against the inside of the wheel drum. Again, the friction created causes the drum, and therefore the wheel, to stop turning.
Power Braking
Today many cars have power braking; a power brake booster helps to force the brake fluid into the cylinders and calipers without much effort on your part.
Antilock/ABS Brakes
If you’ve slammed on your brakes in a car not equipped with ABS you’ve probably seen first-hand how an object in motion tends to stay in motion—and in the case of something as big and unwieldy as a car, not necessarily in the direction you want. This is why your parents always told you to pump the brake—slowing the car down in stages while you steer around whatever hazard you encountered. Antilock brakes do this for you with a computer and sensors that monitor wheel speed much faster than you could. Think of it as many tiny, measured brake pulses so you can keep moving forward (slowly) and steer around potential hazards, as opposed to slamming on traditional brakes and getting thrown all over the road.
THE EXHAUST SYSTEM
Noxious gases. Yes, they’re the end product of the internal combustion engine—though many alternative fuels and engine types are being invented every day to help cut down on air pollution and gas usage.
After the explosions occur in the cylinders, the waste fumes exit through the engine’s exhaust manifold—but not before the positive crankcase ventilation (PCV) valve catches some of the gases that escaped the cylinders into the crankcase, and sends them back into the engine so they can be utilized and reburned. The exhaust then travels down pipes to the catalytic converter, which uses oxygen, heat, and precious metals to convert most of the pollutants into water and carbon dioxide (CO2). The gases that remain chug through the muffler to eliminate most of the noise and then go out into the environment through the tailpipe. An oxygen sensor monitors the fumes and sends the information back to the engine’s computer, letting it know how to mix or rebalance the air/fuel ratio.
The emissions control system is only part of this system.
TIRES
Yes, they count as a “system” too! In some ways, tires are the part of the car you should be most concerned with, since they are directly responsible for your safety. They deserve more than a half-hearted kick now and then to see if they’re inflated properly; at the very least you should understand how to read the information on them and the simple tasks you can perform to keep them at their best.
Learning How to Drive, Take Two
Are you ready to start your engine again?
When you put your key into the ignition and turn it, you close a switch that allows electricity to flow from the battery to the starter, an electric motor that starts turning the crankshaft. This allows the pistons and the fuel to start pumping and the engine itself to take over. The starter then di
sengages itself from the process.
Electricity is also sent to your lights when you turn them on, as well as your radio and anything else that requires juice—and more of it is created from engine power by the alternator, which is then stored in the battery for future use.
The fuel pump delivers gas to the cylinders in the engine, where it is mixed with air and compressed by the pistons. An electric spark in the spark plugs lights this highly combustible mixture, which then explodes, forcing the pistons down, which turns the crankshaft. A computer controls the power and timing of the spark so the engine runs at maximum efficiency.
While this is going on the engine is getting hot enough to melt the metal around it. The coolant is pumped through its water jacket, picking up heat, and then takes it out to the radiator, where it cools off. If you’re cold and turn on the heat in the car, some of this excess warmth gets fanned back into the passenger compartment.
The now-turning crankshaft leads into the transmission, which determines with how much power or at what speed the wheels should turn. To start driving you need to be in low gear, because the car needs a lot more power to start than once it is running on the highway. To shift gears the car must first release the transmission from the crankshaft; this is done by a clutch—or a torque converter in an automatic.
In front-wheel drive, you have a transaxle instead of a transmission, which handles gear-shifting as well as the individual speed of the left and right front tires for when you want to turn.
In rear-wheel drive, the driveshaft continues from the transmission to the back of the car, with a hinge at each end called a universal joint to keep the whole thing flexible and from snapping like a twig if the car hits a bump.
E.J. Braswell Page 2
