What is bleeding brakes

When brake system components get hot, the fluid boils. Brake fluid is hygroscopic, it absorbs moisture. When the fluid boils, the moisture turns to vapor - the equivalent of air in the lines.

What is the problem with air in the lines? Hydraulic brake fluid will not compress in your brake system. It transfers the pressure from the pedal to the calipers. Air or vapor , on the other hand, compresses easily. It gives. It squishes. It absorbs the force. So, when you apply pressure at the pedal, instead of fluid causing the calipers to squeeze, air simply compresses in its space and prevents force from being applied through the lines.

To remove the air in your brake system, a technician will systematically open up a bleeder screw valve on each caliper or on the wheel cylinders in a drum brake system and drain off the air and some fluid.

Care must be exercised so as to avoid sucking more air into the system. If a two-person approach is taken, actions by both technicians must be coordinated so that the bleeder screw is never opened when the pedal is released. The master cylinder reservoir must not be allowed to run dry either. Bleeding the brakes is not necessarily a highly-complex procedure.

But it is an essential one. It also presents some risk. First of all, the vehicle must be raised off of the ground and supported on jack stands or a vehicle lift. Air is much easier to compress than liquid, so bubbles in your brake lines act like a very soft spring in that solid column of brake fluid between your foot and the brake calipers or drums. Bleeding the brakes will flush that air out.

Over time, brake fluid becomes contaminated with atmospheric dirt and abrasive metal wear particles from moving parts in the brake cylinders and calipers. Just like with a pot on the stove, boiling fluid makes springy air bubbles. High temperatures also degrade the alcohol-based fluid itself.

Eventually, brake fluid that was relatively clear when it went in may start to look more like coffee. Antilock braking systems are even less tolerant of contaminated fluid and air than systems without ABS.

The ABS hydraulic pump operates at several thousand psi, forcing brake fluid through very small valves. This can whip air and brake fluid into a latte-like foam, which makes bleeding air out of the system even more difficult. Worse yet, the ABS pump and valves can easily be damaged by those tiny abrasive particles. Fortunately, air that enters the ABS controller can be bled out. However, some vehicles require the use of a special ABS scan tool to cycle the pump and valves to purge all the air inside.

You can avoid these ABS problems by regularly remembering to bleed and flush your brake fluid, which is easy enough to do at home. To properly bleed the brakes, start by acquiring about sixteen ounces of fresh brake fluid. An unopened can has a long shelf life, but an opened can should be discarded within a few weeks. Put the vehicle up on jackstands, removing all four wheels.

Next, make sure the bleeder valves can be loosened. It may help to squirt a little penetrating oil on the bolts the day before you bleed your brakes, especially if rust is common where you live. Loosen these bolts, but leave them closed for now. The jar will be filled with brake fluid to cover the end of the hose. A second person will pump the brake pedal a few times and then hold the brake pedal down while the bleeder screw is opened again. Brake fluid will squirt out and air bubbles will be visible in the fluid.

While the brake pedal is still depressed the bleeder screws will be retightened. The brake pedal will now be released. This process will be repeated until no air bubbles are visible in the fluid. The entire process will then be repeated on each wheel. Our certified mobile mechanics perform over services, including diagnostics, brakes, oil changes, scheduled mileage maintenances, and will come to you with all necessary parts and tools. Our certified mobile mechanics make house calls in over 2, U.

Fast, free online quotes for your car repair. What exactly is bleeding your brakes? How brake pedals are bled Bleeding a brake line can be difficult and should be left to a professional. The following is a quick rundown of the steps involved when bleeding brakes: The brake bleed screw behind each brake is loosened and then tightened again, but not super tight.

Home Articles. When you press on your vehicle's brake pedal, it's brake fluid that does the work. Your leg action moves a plunger in the brake master cylinder that pumps brake fluid through the brake lines and out to the brakes. The fluid applies pressure to the brake pads , which squeeze your vehicle's brake discs or move brake shoes into contact with the brake drums and slow you down.

Brake fluid is the lifeblood of the brake system, and it is designed to work properly for several years before needing replacement. Over time, brake fluid loses its moisture resistance and begins to absorb small amounts of water, which not only reduces brake performance but also can corrode key parts of the system. Replacing the fluid at appropriate intervals is a cheap and effective way to ensure that you're motoring in a safe vehicle, and it also can help you avoid having to pay for expensive brake repairs later on.

An essential part of replacing brake fluid is bleeding the system. That simply means ridding the brake system of trapped air, but some of the old fluid is expelled as well. Fully replacing the fluid is essentially an extended bleeding session.

Bleeding the brake system is something that anyone who's even marginally handy with tools can accomplish at home with the help of an able assistant. Here's how to bleed your brakes in a dozen easy steps. STEP 1: Consult your owner's manual to see which specific type of brake fluid your vehicle requires. It's also good to know at what intervals the manufacturer requires that it be replaced.

There are several different types of brake fluid, and they don't mix well. Head down to the auto parts store or dealer's parts department to pick up the correct fluid before you start working on the brakes.