Hard Brake Petal
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From: Hudson Ohio
Hard Brake Petal
On my '84 with 43k on the clock, the brake pedal is as hard as a brick in the morning. The brakes still work if I stand on the pedal, then after abot 5 minutes, the pedal is normal.
Thanks for any input!!
Thanks for any input!!
Le Mans Master
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From: Tampa Florida
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From: Hudson Ohio
Checked the vacuum to the booster with the engine cold and hot. It started at 17 inches and ended at about 18.5 inches when the engine was at operating temp..
Are you saying to check the booster, put a "T" connecter between the booster and the manifold or use a vacuum pump on the booster at the check valve?
Thanks again.
Are you saying to check the booster, put a "T" connecter between the booster and the manifold or use a vacuum pump on the booster at the check valve?
Thanks again.
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From: Hudson Ohio
Rick,
Thanks for the info.
I have a metal booster. I put a "T" connecter between the booster check valve and the manifold.
Vacuum was 17 inches on start up in park. Depressed the brake pedal and the vacuum dropped to 10 inches and stays there. Goes back to 17 inches when I let off the brake pedal .
Let the temp get to 200 degrees, got the same results.
Any other thoughts?
Thanks
Thanks for the info.
I have a metal booster. I put a "T" connecter between the booster check valve and the manifold.
Vacuum was 17 inches on start up in park. Depressed the brake pedal and the vacuum dropped to 10 inches and stays there. Goes back to 17 inches when I let off the brake pedal .
Let the temp get to 200 degrees, got the same results.
Any other thoughts?
Thanks
Pro
Joined: May 2006
Posts: 536
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From: Humble Texas
Rick,
Thanks for the info.
I have a metal booster. I put a "T" connecter between the booster check valve and the manifold.
Vacuum was 17 inches on start up in park. Depressed the brake pedal and the vacuum dropped to 10 inches and stays there. Goes back to 17 inches when I let off the brake pedal .
Let the temp get to 200 degrees, got the same results.
Any other thoughts?
Thanks
Thanks for the info.
I have a metal booster. I put a "T" connecter between the booster check valve and the manifold.
Vacuum was 17 inches on start up in park. Depressed the brake pedal and the vacuum dropped to 10 inches and stays there. Goes back to 17 inches when I let off the brake pedal .
Let the temp get to 200 degrees, got the same results.
Any other thoughts?
Thanks
My 96 did the samething , it eventualy just stayed hard all the time,
replaced booster and was like new again..you should be able to hear
a hissing when you apply your brakes..
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From: Hudson Ohio
I hear a hiss at all temps when I first apply the brakes. I get the booster to work when the engine warms up and the idle speed gets down to 700 rpm. Was yours not working only when the engine was cold and revs higher?
Thanks again!
Thanks again!
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From: Hudson Ohio
It's coming from the booster. It's the same when the engine is cold or hot. The booster works when the engine gets up to temperature.
If the booster is bad, why does it work when the engine is warm/hot?
If the booster is bad, why does it work when the engine is warm/hot?
Le Mans Master
Joined: Oct 2003
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From: seattle WA
Maybe you should hook up the vacumn guage to the engine, see what the engine health is like. I'd still spray the booster with carb cleaner, or something to see if it's actually leaking, especially when the engine is cold since that seems to be your problem.
Melting Slicks
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From: Austin Texas
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From: Hudson Ohio
Rick,
Here's the results with a vacuum gauge.
I put a "T" connecter between the booster check valve and the manifold.
Vacuum was 17 inches on start up in park. Depressed the brake pedal and the vacuum dropped to 10 inches and stays there. Goes back to 17 inches when I let off the brake pedal .
Let the temp get to 200 degrees, got the same results.
Here's the results with a vacuum gauge.
I put a "T" connecter between the booster check valve and the manifold.
Vacuum was 17 inches on start up in park. Depressed the brake pedal and the vacuum dropped to 10 inches and stays there. Goes back to 17 inches when I let off the brake pedal .
Let the temp get to 200 degrees, got the same results.
Melting Slicks
Joined: Oct 2004
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From: Austin Texas
Your vacuum system is a "closed" system, much like your AC and hydraulic brakes. A drop from 17 to 10 indicates that your system is partially "open" when you step on the brake pedal, or in other words, you have a leak. With the engine running and the car in park, get down and press the brake pedal with your hand. If you hear a hissing sound coming from the firewall behind the brake pedal, the problem is a leaking diaphram. Leaking booster diaphrams tend to be worse when braking is applied, since this action "stretches" the diaphram.
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From: Hudson Ohio
Mike,
I didn't hear any hissing when applying pressure on the brake pedal. That's what was keeping me from replacing the booster. I'll get someone with better hearing to get down there. Hoses are all good and about 2 years old.
Also, heard a high pitch whistle from the intake near the EGR last night. Went away after the engine was warm. Didn't seem to affect the vacuum from cold to hot though.
I am going to take the cross fire apart and seal it before I pull the booster.
thanks again !!!
I didn't hear any hissing when applying pressure on the brake pedal. That's what was keeping me from replacing the booster. I'll get someone with better hearing to get down there. Hoses are all good and about 2 years old.
Also, heard a high pitch whistle from the intake near the EGR last night. Went away after the engine was warm. Didn't seem to affect the vacuum from cold to hot though.
I am going to take the cross fire apart and seal it before I pull the booster.
thanks again !!!
Melting Slicks
Joined: Oct 2004
Posts: 2,510
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From: Austin Texas
One other thing I was thinking about is your vacumm reserve tank. I am not familiar with '84 model year, but later C4's have a round plastic ball the size of a grapefruit to "store" vacumm. The purpose of this storage tank is to assist in maintaining a steady vacumm(or reverse pressure) during peak demand.
Locate this vacumm storage tank and ensure that it is not leaking. Also check all your 1-way vacumm check valves and make sure that air only passes............. 1-way
Locate this vacumm storage tank and ensure that it is not leaking. Also check all your 1-way vacumm check valves and make sure that air only passes............. 1-way