Brake/Servo issues

[John_Mc]

I have braking problems. When I put brake pressure on, I get a "pffft" noise and braking goes weak, but returns when I let up and reapply. When I get the "pffft" and hold down, the hissing remains constant and comes from my footwell, not under the hood, and the engine revs differently. Obviously a vacuum leak, so I suspect my servo is in need of repair. I see repair kits but I don't know where to check to see if the repair kit is all I need or if the whole servo needs replacement/reconditioning. I also see that there are aftermarket units available or original ($$$). I see that Ted Schumaker sells reconditioned kits, but I read on TRFs site that those units do not rebuild well. This all gets very confusing to me. Any idea how to go about diagnosing what I need and what the best parts to get are? Any help and experience would be most appreciated.

PS I replaced the master cylinder a few years ago after it started leaking. I am not sure if I got original or aftermarket since I wasn't aware of all the different units available at the time. Is there a chance this is a master cylinder issue rather than a servo issue? I'm guessing not since there is the vacuum leak. TIA.

 

[BRSLimited]

Does the engine sound change when you apply the brakes? If it's a vacuum leak it should either rev up slightly or dip down slightly (depends of if it's running a hair rich or not). You can try while holding the brake pedal down a little climbing under there with a can of carb cleaner and spray where the pedal pushrod goes thru the firewall. If the booster is leaking from there the engine note will change to indicate a vacuum leak. This also works to diagnose worn throttle shafts, leaking intake gaskets, cracked emission hoses, etc.

 

[Brosky]

If you are hearing it inside the car, it is most likely the vacuum booster diaphragm. I had mine rebuilt by Brake Parts for $125 including the shipping and powder coating.

 

[tdskip]

John - Power Brake Exchange in San Jose will likely take care of this for under $200 (call first).

If there are issues you can just zip over there.... in an other car

 

[TR3driver]

The minor repair kits only replace the check valve and gasket under the hood, so not likely to solve your problem, IMO.

Rebuilding the servo yourself is not out of the question, but does require some special tools and such, plus you have to source the parts (which may or may not be readily available).

You might check with your FLAPS first (especially if there is an independant store around, not Autozone or O'Reilly). Sometimes they can send them out for rebuild cheaper than the same rebuilder would charge you directly.

 

[Andrew Mace]

My local NAPA store has been extremely helpful of late, being more than willing to dig around a bit as needed to get what I need. Case in point: my son's 1981 Subaru recently developed a charging system problem. I was pretty sure it was the (external) voltage regulator, but I decided to pull the alternator and drop it off at the NAPA store, where they could send it out to be checked and repaired as needed. They originally told me it might be the better part of a week (which was fine, since it would take time to get a new regulator), but I had a call the next day telling me "my alternator was in"! Turns out that there was a rebuilt on the shelf where they sent it, and they came back with that...for less than $40!

Now getting the regulator turned out to be an ordeal of great magnitude, but it had nothing to do with NAPA...and I'm not going to bash any vendors here. It will suffice for now to note that I finally got the regulator, and I may get to keep three brake hoses for a '94 Ford F-350 Diesel pickup! :shocked:

 

[John_Mc]

Renewing this old thread with some follow-up:

I took my servo to Power Brake Exchange (thanks for the tip, tdskip!) and the guy had it repaired for me in under an hour. The problem was a torn diaphragm as suggested above, caused by gasoline in the booster from a bad check valve. Is this a common problem? Anyway, he replaced the check valve as well and gave me an additional inline valve to use. Anyone have similar experience?

 

[tdskip]

Glad they got it sorted John.