Hello, I just bought a 1990 civic. The brakes feel pretty decent about 90 % of the time then randomly they will just go to pretty much the floor and barely stop the car. I can fix this by pumping the breaks a bunch of times and sometimes restarting the engine. Usually it will pump back up to pressure. To me this sounds like a master cylinder that has a failing seal, only sometimes letting fluid slip past, so I change the master cylinder yesterday. Brand new one from oriellys, annnnnd after hours of bleeding I still have the same problem. What could it be? Is it possible it could be brake booster related? to me the brake booster would make sense but at the same time it does not, if the booster were to fail I hear people say they get a hard pedal not one that hits the floor. I guess it could be a brake line that bulges up but I cant replicate it by stomping the brakes as hard as I can and I kindof doubt that thats it.

 

Looking for leaks would be the next thing to look for. Particularly around the rear slave cylinders.

 

@toxictom did you ever figure out your issue? This happened to me today, super weird. Looked at all the lines, master cylinder, fluid level. Nothing out of the ordinary. Curious if you were able to find the issue.

 

yea, found out it only happens on left hand corners, when I corner on the left hand side for some reason the rubber brake hose gets pinched inbetween the caliper and the shock. strange. still havent fixed it lol... just dont take full cut corners. got a few things more important to do on it right now (finish my mpfi and start tuning with my ostrich) you could potentially have a leaky master tho if u genuinely just randomly lose ur brakes.

 

Thanks for following up. This was exactly what I was suspecting with my set up. The StopTech lines I have up front don't fit perfectly like stock and I suspect under hard corners getting pinched a little.