Power Brake Boosters
Virtually every modern car uses power (or hydraulic) brakes, but not many people actually know what that term means, or what power brake boosters are. Before power brakes, older cars used drum brakes, which work similarly, but did not require a booster because of their design. Drum brakes are still used, but mainly for back wheels (the front wheels do most of the braking) and for the emergency brake. They are generally less efficient and harder to use than power brakes, which is why almost all modern cars use disc brakes, at least on the front tires. Another type of brake is the mechanical disc brake, which uses cables in a similar way to bike brakes, but those are rarely seen anymore.
Power breaks use discs, but there is a pretty large difference between the mechanisms in power brakes and mechanical disc brakes. Mechanical disc brakes, as mentioned earlier, are mainly used in bicycles. The foot pressure needed to actually stop a car would exhaust most drivers, to the point where they aren’t practically usable except in some situations. Power, or hydraulic, brakes have a system which ensures that braking is much easier on the driver.
This is where the power brake booster comes in. Anybody who has looked under the hood of a car has seen a power brake booster – it’s circular, black, and located right behind the engine. It should also have a metallic tube-like object running out of it. What power brake boosters do is apply a vacuum from the engine to the braking force your foot applies.
In essence, when you press on the brake pedal, you’re applying force to the master cylinder, but not enough to actually stop the car. At this point, the brake booster comes into effect. Gas-powered engines naturally create a vacuum by design, and the brake booster basically opens up to the vacuum. This creates a chain reaction that results in increasing the amount of pressure applied on the brake disc. The vacuum created by the engine and channeled through the booster is applied back to the master cylinder, which controls the entire braking system.
Many braking problems can come from a broken brake booster. When a brake booster is going bad, there can be a few resulting symptoms. Some people will only hear some whistling. This means that there is probably a minor air leak where the vacuum induces pressure. In that case, it probably only has a minor effect on the brake’s actual performance, but the performance will begin worsening. A leak in the booster means that there is pressure on a weak spot of the device. More subtle problems can show themselves in only performance, and it’s hard to tell brake booster problems from other problems in the braking system by gauging performance.
Fortunately, there are some good tests you can do on brake boosters to check their performance. First, if pressing on the brake pedal is getting harder, it is almost certainly a problem with the booster. If you think the problem is with the booster you can perform a test on it by performing a vacuum testing check. This will make sure your booster is taking in an appropriate amount of pressure from the engine. For more information on how to do this test, consult your car manual for advice. Some more modern cars might come with booster check valves, which won’t require any real mechanical skills to perform. For other cars, it will likely involve placing a hose in the right area of the engine or booster. If your booster needs to be replaced, it will most likely require a very good amount of car skills to replace.
