View Full Version : Brake Booster Problem - continued

06-10-2015, 06:21 PM
I have the Ford manuals for my 94 SC. My brakes require excessive effort on the pedal to stop. (Let's just say that if grandma drove the car she'd rear end someone because she couldn't press hard enough on the pedal to stop the car). I've run the diagnostic tests in the manual and all signs point to break booster. Before it failed completely I was hearing a hissing sound from the floor each time I depressed the brake pedal.

Looking for confirmation that I'm on the right track here. If I am do I go with the ACDelco part from Rockauto or do I do the Autozone part?

06-10-2015, 06:47 PM
Hissing sound and hard pedal both point to a leaking booster, I think.

RockAuto shipping might be a deal breaker for that thing. I'd get best price with best warranty from local vendor in that case.

06-12-2015, 12:33 PM
It was the brake booster. Replaced it yesterday. Pedal feel is completely normal now (except for the need to bleed the system).

That raises the question - in my Ford manual it states I need some fancy test equipment to bleed the ABS brakes on the car. I obviously don't have that. I've read some posts that suggest bleeding the brakes with the car running. Is that the right thing to do in this instance?

06-13-2015, 07:52 PM
Okay - so the hiss is gone, the pedal "feels" normal but there's still limited power assist braking. I hear a hiss in the corner where the booster is so I know there's some sort of leak but I'm drawing 18 inches of HG right at the input to the booster. The book says you need 12 inches of HG to make it work. Have any of you had the seal between the booster fail? How about the seal between the push rod sensor inside the booster?

Anyone able to offer a suggestion?

06-14-2015, 12:44 PM
Both sets of seals can fail.

TYPICALLY, a brake booster will fail when the master cylinder starts to seep brake fluid - which rots out the rubber.

But yes, they can just fail due to age.


06-14-2015, 10:27 PM
Thanks for the response. I did figure it out. I was curious to see what was behind the push rod sensor and took it out. When I put it back in the booster I failed to put the gasket on it. Had a vacuum leak because the seal wasn't there. Put the seal in and the car is golden.

Managed to get the new rear springs in and boy does the car handle like new again!