alydar66

Hi, I have a 1989 Cougar with non-ABS brake system. The brake pedal goes to the floor when I first press on it , but after pumping the pedal 4-5 times the pedal comes up about half way. Ive replaced the brakes, replaced the master cylinder and bleed the system and I am still having the same problem. The only thing left would be the booster unit. Could that cause the problems Ive been having? Does anyone have any other ideas that may be causing my problem? Thanks for any suggestions.

 

backlash1

Hi
Definitely NOT a brake booster problem. When the booster fails, the pedal feels really hard because there's no assistance, it will have a similar feel to pumping the pedal with the engine switched off. The symptoms you describe are typical of air in the system, and the fact that you can recover pedal by pumping it means there shouldn't be any leaks. Cougars are notoriously hard to bleed, we use a machine that pressurizes the system (about 5psi) as the only way to bleed them properly. How are you going about bleeding your brakes?

marc

alydar66

Im doing it manually one wheel at a time. When the car is not running the pedal is hard and it holds, but as soon as I start the car the pedal goes to the floor when I press on it.

alydar66

I also forgot to mention that when I press down on the brake pedal I can hear a big puff of air. And after I pump up the pedal I can hear a slight hissing sound while pressing down on the pedal.

backlash1

OK. So this means that you're doing it on your own, and just bleeding the system by gravity ? If so, get someone to assist you. Tell them to sit in the car and pump the pedal 4-5 times and hold it down. Then you open the bleed nipple and let the fluid run for a few seconds, WHILE the other person keeps the pressure on the pedal, even if it sinks to the floor. Close the nipple and then tell the other person to release the pedal. Repeat this cycle 4/5 times per wheel and move on to the next. Always start at the rear caliper on the opposite side of the master cylinder and go diagonally from there until there's no air coming out of the nipples and the pedal feels normal again. Also keep the engine off while doing this bleeding procedure so as not to damage the master cylinder from pressing too hard on the pedal. Hope this helps.

...And this actually means that your booster is working. cheers

marc

ThunderCat84

i have a 84 cougar and what you are saying is just the problem i had
pedel falls to the floor pump it a couple of times then the pedel stays stiff for a while then back to the floor. it was also hard for me to stay stoped on hills bc i converted it to standard. But i just fixed the problem today all normal again..all i did was replace the booster. the hissing noise is air leaking out of the booster. the booster leaks air into the master cylinder idk how it does it but that was my problem..hope you fix it