I've searched for the answer prior to the post, did the suggested fixes, yet the problem still persists. Integra GSR brake swap on a Civic, has been on the car for over 15 years, but the car sits a lot. Trying to get in back road worthy and have had continuous brake issues. After driving for abut 10 minutes, the pedal pumps up and the front brakes lock up. Here's what I've done so far. Replaced brake booster with new booster. Replaced master cylinder with one from a junk yard. Removed both front calipers, disassembled and cleaned, greased, reinstalled. Flushed the fluid through 2 times. Adjusted the booster rod to brake pedal. Check valve is working properly in vacuum line. At this point it seems like the only other possible part to replace is the proportioning valve since everything else has been replaced. Any thoughts or suggestions aside from everything I've already done would be greatly appreciated.

 

Forgot to mention one thing. We I removed the vacuum line, it didn't release any pressure. It seems like the booster is building pressure and won't release it. Thoughts?

 

Have you considered that the calipers might just be sticking? When they sit for a while that can happen. I once pulled of a low mileage set of calipers from a '97 in a salvage yard to swap out my leaking ones (instead of rebuilding them) and for the first 30-40 miles the front left kept sticking and my rotor was glowing orange. I just pushed through it though, driving slowly on low traffic roads and the problem eventually fixed itself with enough driving. They still work perfectly now after about 35k miles. Try driving some more, or consider that they might need to be rebuilt. My thoughts are that you're having the same issue I was because the car has sat a lot.

 

The calipers have been disassembled, clean, greased and put back together. They were moving well after greasing them.

 

bent rod on the brake mc?

 

Update, replaced the booster with one from a junk yard and all is well so far. A heck of a lot of work to figure out what was wrong. Guess I'll return the new one and get my money back.