I am having a real hard time stopping and when I push the brake pedal it seems very stiff and then there is also a hissing noise that I can hear by the pedal it seems. I was just wanting to know what my problem might be ??? It is a 85 by the way.

 

The brakes are vacuum assisted. You have a vacuum leak somewhere. Find it . Fix it. End of problem :)

 

C4s vacuum boosters have a history of failure. There seems to be a few
different failure modes, but your description of a stiff pedal accompanied
by a hissing sound is a classic.

Before condeming the booster, check for leaks in the line from the
manifold that provides the vacuum source like BritVette recommends
above. If the hose on your '85 is original, it may have failed. There is
a check valve at the booster and I have seen other posts mention
a check valve at the manifold (but I believe my car just has a fitting
the hose connects to at the manifold side).

Some times a booster leak will be internal (failed diaphram), others
have reported big visible cracks in the lower side of OEM plastic housing.

If the booster is bad and you elect to replace it yourself, look for threads
that describe the process. You'll want to remove the driver's seat and
gather a 13mm deep 'wobble' socket, and some socket drive extensions.
Sears sells a short extension that works with a conventional socket to
become 'wobble' combination. A swivel will work but the work area is
difficult to reach to control socket flop.

It is not considered necessary to disconnect the brake lines from the
master cylinder but check the rear of the m/c for seepage while it
is off the booster. Replace it if seeps are found or if there is sludge
in the reservoirs.

Some time spent adjusting the pedal rod during reassembly can optimize
brake feel.

A search here will bring up many threads with recommendations. I believe
I've seen favorable reviews of rebuilt units from Autozone and Pep Boys.
A recent thread mentioned about how the braking improved so much
the owner now considers the pedal 'sensitive'.

If you are interested in taking the road less travelled, have a look at
the HydroBoost by HydraTech. These are a popular upgrade with
the C3 crowd. Talk to Paul there for information about use in your
type of C4 application - he is VERY helpful and a pleasure to deal with.

http://www.hydroboost.com/




[Modified by Slalom4me, 8:29 AM 7/15/2003]

 

Slalom4me or anybody do you have a picture of the check valve at the manifold or the fitting the hose connects to at the manifold side? I dont know what I am looking for. Itried to look this morning but I could not figure it out on my own. Also when I push down the brake pedal the louder the hiss gets.

 

If you look at the brake booster, there is a fitting sticking out of it with a hose attached. That is the check valve. Follow the hose to the intake manifold and it should attach to a fitting on the intake manifold.

Has the car had a rough idle as well? the vacuum leak might contribute to that.

Anyway, it sounds like a booster problem. I drove like that for 5 months, and recently replaced the booster in April. It's like driving a new car with brakes, lol. Good luck, easy fix, but a PITA to do. :cheers:

 

Like the guys have said, you must be a contorsionist, have very tiny hands and some really good luck when trying to put the new booster in. The steering column mount on mine dropped down about 3/8" and it took wifey and I about and hour to get it in. You might also want to have a couple of spare shouldered nuts that fit the booster. If you drop them, the Corvette Gremlins hide them. Still have not found the 2 original nuts. The wobble socket is a great idea. Good luck

 

Probably the best diagnostic tool you can buy is a vacumn pump with a gauge on it. You can find vac leaks from everything from brakes to cruise and in between. having one has saved me a lot of time and frustration.
:yesnod:


[Modified by Southern Comfort, 2:53 PM 7/15/2003]

 

Hey, but I bet your french really improved! My vocabulary always
grows by leaps and bounds on such occasions (Madam Saborin
must be so proud!)

 

Mine must be worse than yours was because its not safe to drive mine right now. The damn car just wont stop and the harder I push the louder the hiss gets.

 

Just went through this a month ago. Just had the car teched for an autocross and when I left the parking lot, no brakes. If you hear the hiss while in the car the booster is bad. You will also notice an increase in idle speed when you press the brake pedal (vacuum leak). Only fix is a new booster. GM used to have a rebuild kit for the booster but discontinued it last year. The job is near impossible if you're large. I got my wife to work on the inside after I took the seat out. When you put the new booster in be sure to hook the pushrod to the pedal before securing the booster to the firewall. I didn't and had to take the thing loose again because the pushrod will not fit on the pedal when the unit is secured first.

 

I am a big dude so I will pay a shop to fix it .Does anybody have an idea of what I might have to pay?????You just cant win with these cars can you...lol

 

:iagree: :iagree: :iagree:

 

Doesn't have anything to do with being big. I couldn't fit my hands up there either. You have to use something like grease etc... in the end of the socket when you take off the nut, the grease will hold it in the socket. When I reinstalled the nut, I taped it to the socket. There are only 2 nuts, and a clip for the pushrod to pedal connection inside the car, 2 nuts on the master cylinder. Pay attention to the pushrod length on the replacement booster. The little nut on the end that adjusts the length has a great deal to do with pedal height, effort and brake feel. Good luck :cheers: