'96 hard brake pedal sometimes....
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Intermediate
Joined: Sep 2005
Posts: 48
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'96 hard brake pedal sometimes....
So, I have a hard pedal sometimes and I do hear some hissing. It's not happening all the time but more often it seems as of late. Is it the booster or master cylinder or both? Can it just be a vacuum leak? Looking for some advice... Thanks guys!
Race Director
Joined: Oct 2005
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From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
Yes, the hissing you hear is a vacuum leak.
It could be the diaphragm in the brake booster, the vacuum hose between the intake and booster, or one of the fittings on either end of the hose.
With a vacuum leak, there won't be much (if any) "Power" in the power brakes.
Your pedal will be hard like you describe. And since these brakes were designed to be power assisted, it will be even worse than the old style non power brakes.
It could be the diaphragm in the brake booster, the vacuum hose between the intake and booster, or one of the fittings on either end of the hose.
With a vacuum leak, there won't be much (if any) "Power" in the power brakes.
Your pedal will be hard like you describe. And since these brakes were designed to be power assisted, it will be even worse than the old style non power brakes.
Drifting
Joined: Sep 2010
Posts: 1,571
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Apparently 9 times out of 10 the problem is the booster itself not a leak somewhere else. Replace that and your brakes will be fine. If there's no fluid leaking where the MC bolts up to it then no need for a new one.
Heel & Toe
Joined: Oct 2010
Posts: 15
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Before you go changing the booster check for vac leaks, especially the fittings under the pass side fuel rail cover and the vac ball in front of the left front wheel. No need to mess with the master cylinder in any case.
