I have a 94 Pontiac Bonnyville that's leaking brake fluid. Recently the brake warning light came on and I noticed the fluid was low. I filled it again but it's slowly leaking.

The fluid is leaking at the point where the bottom of master cylinder meets the booster. There's an 1/8" wide bead of fluid dripping straight down and over the booster and then onto the ground. It doesn't appear that the fluid is leaking from the booster where it meets the firewall.

The brake pedal feels fine and doesn't sag to the floor while waiting in traffic. It doesn't stop like a Porsche but the stopping performance seems fine.

My question is, should I replace the booster as well as the master cylinder? How can I tell if the booster is bad?

This car is a ticking timebomb and i'm hoping to have it for less than 6 more months. However I don't want to be reckless to save a few bucks.


Just need to replace the master cylinder, the booster should be fine. The piston in the master cylinder is bad and is leaking against the booster. That's the only place for the fluid to come out.

  • Thanks again for the answer! I swapped it out and all is well. Nov 9 '14 at 17:54

Any brake fluid leak what-so-ever should be repaired immediately. Your master cylinder requires to be changed before driving the vehicle at all on the road. That is unequivical.

  • 100% agreed! I did drive it back home after the caution light came on, filling up the reservoir on the way home. Re-reading my post I can see how it looks like I didn't want to replace the master cylinder but I just didn't want to replace the booster as well if the booster wasn't necessary. Nov 9 '14 at 17:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.