The fix, trouble shoot, process of elimination.
Power booster vacuum and valves.
Proportioning valve.
Some tall cams produce no usable vacuum, auxiliary vacuum pump option. Measure intake vacuum.
With vehicle off pump the pedal a couple of times and while still pressing on the pedal crank the vehicle and see if the pedal drops at all . If not as ANTISPAM noted you are not getting vacuum . Make sure check valve is good .
SOURCE: Brakes no longer work in 1989 Chevy half ton pickup 2 wheel drive 350cubic inch
change dump valve under master cylinder
SOURCE: Front Brake Pads locked up on Rotor
Have the brake pads been so very work they are down to the metal? This could cause the caliper piston to extend too far and not be able to retract properly.
Calipers Fail mostly from a cut in the rubber boot around the pistion dirt and debris get in there and rust the piston and it cannot retract properly Do they retract after they cool Down? if so the brake fluid has "boiled" if brake fluid is not changed about every 24,000 miles condensation builds up and lowers the boiling point of the brake fluid causing this problem.
Tell me does it happen after a long drive or siting a long time in heavy bumper to bumper traffic in hot summer weather? I recommend a complete brake fluid flush an change the calipers with NEW ones ot rebuilt and use dielectric grease on all points of metal to metal contact between the caliper an the mount bracket and thee ends of thee pada n the slide points they ride on and the pins that go through thecaliper and thread into the mount only dielectric not regular grease it will cause sticking and a worse problem than you have now.
SOURCE: bleed brakes but no pedal
Good! You bled the master cyl. before installation! The proper order of bleeding the lines, is to start with the wheel the greatest distance from the master cylinder. Then work your way to the next greatest distance, and last, the closest wheel. Make sure all air is removed from the lines before you proceed to the next wheel, and frequently check the master cyl. level, because, as I'm sure you know, if you **** in air at the master, you have to start all over again. I'm assuming you don't have a power bleeder, so with a helper do this with car running (make sure it's on safety stands and not going to fall on you!) Pump pedal 3 times, no need to mash the pedal into the floor, just 3 pumps 1/2 way down, hold 3rd pump at half way down level while bleeder is opened, when flow is about to stop at bleeder, close bleeder and repeat til no evidence of any air. Let me know how it goes and if you need any help.
SOURCE: Spongy brakes
So long as the brake booster is working, test it by turning on the engine, press the brake pedal all the way down, then shut off engine keeping your foot on the brake pedal, if the pedal comes up slightly pushing against your foot then the booster IS working.
Did you BLEED the brakes??????
SOURCE: stuck calipers
Brake lines are not releasing fluid back to master cylinder. Open bleeder and see if wheel will turn. If it does replace brake line to caliper
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