Loosen these bolts, but leave them closed for now. 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. You’ll need a box wrench that fits the bleeder bolt, as a crescent wrench or vise-grip could strip off the edges of the bolt and make it impossible to loosen. Next, make sure the bleeder valves can be loosened. Put the vehicle up on jackstands, removing all four wheels. An unopened can has a long shelf life, but an opened can should be discarded within a few weeks. To properly bleed the brakes, start by acquiring about sixteen ounces of fresh brake fluid. You can avoid these ABS problems by regularly remembering to bleed and flush your brake fluid, which is easy enough to do at home. However, some vehicles require the use of a special ABS scan tool to cycle the pump and valves to purge all the air inside. Worse yet, the ABS pump and valves can easily be damaged by those tiny abrasive particles.įortunately, air that enters the ABS controller can be bled out. This can whip air and brake fluid into a latte-like foam, which makes bleeding air out of the system even more difficult. The ABS hydraulic pump operates at several thousand psi, forcing brake fluid through very small valves. Eventually, brake fluid that was relatively clear when it went in may start to look more like coffee.Īntilock braking systems are even less tolerant of contaminated fluid and air than systems without ABS. High temperatures also degrade the alcohol-based fluid itself.

Just like with a pot on the stove, boiling fluid makes springy air bubbles. Over time, brake fluid becomes contaminated with atmospheric dirt and abrasive metal wear particles from moving parts in the brake cylinders and calipers.īrake fluid also absorbs moisture from the air, which can lower its boiling point enough to make it boil at the end of a long downhill grade or some other scenario such as a track day where you’re using the brakes repeatedly or for a long time. While you’re bleeding out the air bubbles, it’s best to flush all of the old fluid out of the system and replace it with new stuff. Bleeding the brakes will flush that air out. 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. If you let your brake pads wear so thin that the brake fluid level drops too low in the master cylinder reservoir where you fill the system with fluid, this can introduce some bubbles into the brake lines. In a disc brake, fluid pushing into the brake caliper is what moves your brake pads inward to clamp down on the rotor and slow the car using that friction.Īs pads wear down, it takes more fluid to press them onto the braking surface. Pressing the brake pedal shoves brake fluid out to the brakes at the four corners of your car. Your brakes are a hydraulic system, which means that fluid makes them work.

There are a few different ways air can enter your braking system, and all of them involve brake fluid. It’s time to replace that old brake fluid and bleed all of the air out of the system. These are the telltale signs of air in the braking system, which happens over time with use. Your pedal probably feels spongy and it’s often hard to feel exactly when the brakes start to bite. Fresh, thick pads should have brought that pedal back up where it should be, but it didn’t. Maybe you noticed that you still have to press your brake pedal far into the floorboard to stop even after swapping out your pads. Not even new brake pads can save you from the dreaded soft brake pedal.

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