Why do brakes squeal or squeak?

Brake squeal is the result of a high-pitched vibration of the brake pads. This vibration occurs because the pads are not properly insulated from the caliper or secured to the caliper. Brake pads come from the factory with anti-rattle clips, pad insulator shims, and sometimes a silicone backing that literally glues the pad to the caliper to keep the pads secure and to prevent rattle or vibration.

Sometimes brake squeal is the result of the composition of the brake pads being too hard. These hard, smooth surfaces rub against each other, resulting in the "nails across a blackboard" syndrome. If this is the case, replace the pads and resurface the rotors. That should stop the squeal.

Finally, if the brake rotors are not re-surfaced when a brake job is done, it results in squeal. When brake pads are replaced, the rotors must be resurfaced with a non-directional finish applied to the rotor face to ensure proper pad break-in. In order for the pads to break in properly, pad material must be worn off (this happens when the rotor has been resurfaced properly and the brakes applied for the first 500 miles or so).

When brake squeal is evident, the tech should start with ensuring that the pads are properly secured and insulated to the brake caliper, and the anti rattle clips are installed to stop pad rattle. In addition, the tech should make sure the rotors were properly resurfaced for pad break-in. Finally, the pads themselves could be the culprits if all the aforementioned are in place.

What is the difference between "outside" and "recirculation" settings on your car's AC?

"Outside" setting means just that, fresh outside air is being fed into the vehicle's cabin along with the climate-controlled air that the HVAC system is feeding into the cabin. "Recirculation" means that the air being fed into the vehicle's cabin via the HVAC is being recirculated without adding fresh outside ambient temperature air.

What is the difference between premium and regular gas?

The difference between premium and regular gas is the octane rating. Octane is the measurement of a gasoline's volatility factor in the combustion chamber environment. The lower the octane, the more volatile; the higher the octane, the less volatile (more stable).

Low octane fuel is more apt to pre-ignite or ping inside the engine. Some refer to this phenomenon as "engine knock." Engine Knock occurs when the fuel ignites in the upper regions of the engine before the spark is introduced at the high point of compression. To understand what's happening, you must first have a basic understanding of how an internal four-stroke internal combustion engine works.

On the first stroke of the four-stroke cycle, the intake valve opens, the piston travels down, and the injection system injects a perfect air/fuel mixture into the combustion chamber. The suction or vacuum produced by the downward stroke of the piston is what draws the air/fuel mixture into the engine; this is called the intake stroke.

Now that the combustion chamber is loaded with air and fuel, the valves both close and the piston travels back up, compressing the mixture tightly; this is called the compression stroke. Compression of the mixture makes it highly volatile.

At the precise time that the mixture is at its greatest compression, an electrical spark is introduced into the chamber through the spark plug. This spark ignites the mixture and forces the piston downward; this is called the power stroke.

Finally, the exhaust valve opens and the piston travels back up, pushing the burned exhaust gas out of the chamber; this is called the exhaust stroke. This process repeats over and over, producing power in the engine.

When pre-ignition occurs, the air/fuel mixture is ignited as it is introduced into the combustion chamber before it has been compressed. Pre-ignition of the mixture hammers away on the tops of the pistons, the faces of the valves and the cylinder heads. Over time, irreversible damage occurs and major engine work must be done to correct it.

Today's engine management systems use a knock sensor to monitor combustion chamber pressure. When the knock sensor detects excessive pressure in a combustion chamber, it retards ignition timing, thus reducing or eliminating pre-ignition.

High output engines run with much hotter combustion chamber temperatures. Therefore, when low octane fuel is used (more volatile), the performance system cannot make the adjustments and pre-ignition can occur. If your owner's manual suggests using high-octane fuel, then use it or suffer the consequences of prolonged use of low octane fuel ... engine damage.

Should I let the car warm up before driving, or cool down after driving?

In days of yore when carburetors were used along with standard ignition systems, it was a good idea to warm up the engine for 10 minutes or so before embarking on a trip because carburetors had what was called a "Cold Start Circuit." This "circuit" used a choke (a butterfly valve located in the top of the carburetor). The choke was controlled by a bi-metallic spring that expanded and contracted, depending on the temperature.

When cold, the spring would contract, pulling the choke closed. When the choke was in the closed position, the carburetor would suck in more raw fuel than when the choke was open. Engines needed a much richer fuel mixture to start when cold, hence the closing of the choke on cold startup. After the engine warmed up, the spring would expand, the choke would open, and the carburetor would run on the "Idle and Power Circuit," using much less fuel.

Why this history lesson? Because today's cars use EFI (Electronic Fuel Injection) instead of carburetors. With EFI, the system senses when it's cold outside and makes adjustments to fuel delivery for cold start and run conditions. The computer system monitors engine parameters while running and makes adjustments to fuel delivery and ignition timing for optimum performance, regardless of the engine temperature. Therefore, warm up or cool down really doesn't matter on today's cars. Allow the engine to run a few minutes when it's very cold before proceeding so that the oil is flowing, then off with you!

How does the battery stay charged?

Automotive charging systems keep your car's battery charged at all times. The battery provides the heavy cranking amperage necessary to crank the starter motor to start the car. Then the charging system provides a steady feed of voltage and amperage to keep the battery in perfect health for the next time you have to start the car or use an electrical device inside the car.

Also, the charging system provides the steady minute voltage necessary to operate the performance system of your car. When you start the car, a heavy amperage loss occurs on the battery; this is called a load. After the car starts, the alternator recharges the battery with voltage and amperage.

Perfect charging parameters range between 13.8 to 14.2 volts and up to 200 amps, depending on system requirements and alternator output capacity. All this is controlled and monitored by the voltage regulator. When the regulator "sees" that the battery either needs more or less voltage, it makes adjustments to keep the delicate balance of battery charge.

Why do car mufflers "smoke" on cold mornings?

The "white smoke" you see coming out of the tailpipe in the morning is the result of condensation buildup in the exhaust system. When the hot air of the exhaust from the engine meets with the cold air inside the exhaust system, a cloud forms, resulting in the white smoke you see coming from the exhaust.

How do ABS brakes actually work? How do I know when they're working?

ABS uses wheel speed sensors, a hydraulic control unit, and a computerized electronic control module, which is the "brain" of the system. When the brake pedal is applied, the electronic control module monitors the speed of the wheels through the wheel speed sensors. If the control module detects that one or more wheels are about to lock up, the module signals the hydraulic unit to control hydraulic pressure to that wheel or wheels. This varying of pressure is much like "pumping" the brake; only with the ABS system, the wheel that is locking up (causing a potential loss of control) is the only one being controlled, while the rest of the wheels are free to roll. This maximizes vehicle steerability.

Here are a few things you may notice the first time you use antilock brakes:

· When the pedal is applied and ABS is activated, the pedal may feel harder than usual; this is normal.

· The pedal may seem to ratchet or pulsate (vibrate), or there could be a combination of these sensations; this is also normal.

· Finally, you may hear a noise that sounds like a motorboat engine; this is the hydraulic control unit operating; again, this is normal.

When driving a car with ABS brakes, remember to:

· Maintain the same safe stopping distance from the vehicle ahead as with conventional brakes. ABS will not make the vehicle "stop on a dime."

· Do not pump the brake. Just apply firm, constant pressure and let ABS do the work for you. You may feel a slight vibration or hear noise as the hydraulic control unit functions. Be ready to push the pedal further if it travels closer to the floor.

How much water does it take before my car will hydroplane?

Hydroplaning or aquaplaning is a phenomenon that occurs when a layer of water builds between the footprint of the rubber tires of the vehicle and the road surface. When this happens, the vehicle can't respond to control efforts such as steering and braking.

According to laboratory tests, hydroplaning occurs on a wet road surface at speeds of 50MPH or higher. The deeper the water, the worse it becomes. You're driving along in the rain, and suddenly your car is out of control, acting as if it were on ice. What is happening? A thin sheet of water has formed between the tire tread area and the road surface. Your vehicle has become a powerful sled and you're along for a wild ride!

Three main factors that contribute to hydroplaning:

· Vehicle speed: As speed increases, wet traction is reduced, and thus the chance of hydroplaning increases.

· Tire tread depth: The more shallow the depth, the less the tires are able to resist hydroplaning.

· Water depth: The deeper the water, the sooner the tires will lose traction.

If you find your car hydroplaning:

· Do not apply the brakes because braking is ineffective when hydroplaning and will cause the vehicle to skid even more.

· Do not turn the steering wheel. The vehicle is moving uncontrolled on a sheet of water; trying to steer out of it could result in a crash.

· Hold the wheel firmly and do not steer in any other direction but straight ahead. This is the best way to "ride it out."

· Ease your foot off the gas (helps to regain traction) until the car slows and steering returns to normal.

· If you need to brake, do it gently with light pumping actions. If you have ABS brakes, the system will do this for you. Just apply steady, even pressure to the brake pedal and the system will take care of the rest.

· Once your vehicle's tires come in contact with the road surface, you should be able to regain control.


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