deanh22a

So, I'll just be driving and my brakes randomly start depressing themselves. I constantly have to push my brake pedal up with my foot when I feel the brakes tightening. Also, the pedal is usually hard. I barely press it and the car acts like I slammed on the brakes. occasionally it feels normal, at random times. I've done the brake tests where you sit and press the brakes with the engine off and then running etc, and there's no signs of fluid leak and the booster seems to be working normally. And ideas?

toyomatt84

iTrader: (1)

You may have some issues with the ABS system (depending on year/model of the car).

deanh22a

My car doesn't have abs.

toyomatt84

iTrader: (1)

Hard to give you any sort of information, without knowing the year and model of the vehicle.

bandit67

I have resurrected many older Civic clunkers....93-95 models with lots brake problems......but never the problem u describe. Usually , the master cylinder always works....just starts leaking inside the car or out. I have never had to replace a booster even though some of these clunkers had sat up for many years. My local salvage yard has lots of Civics and I very seldom see one with the booster pulled, but I think I would replace your booster and put in a new or good looking used master cylinder. Engine vacuum pulling on the booster internal rubber seal is what gives the power assist. Yours seems to be allowing the force to be applied most all the time. i.e. tight brakes. If something is keeping the pedal from fully returning to back position, then the booster will apply braking force.

DumpdEJ6

^^^ Good info here. Also, check your check valve (haha). There should be a one-way check valve inline from your brake booster to your intake manifold, if that valve gets stuck or clogged, it will result in the symptoms you've described.