No brake booster assist when started cold

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  #1  
Old 12-15-07, 04:17 PM
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No brake booster assist when started cold

1999 Intrepid
Cold morning problem
Got in car and no power brakes.
Took hose off the booster and there was lots of vacuum.
Let it warm up and then when the heat was on the floor they came back.
When they came back I could hear the "noise" of air when I pushed on the brakes.
I kept working them.
Noise went away and brakes are fine now.

I would say that it is the booster with a hole in the diaghram but why just when it is cold?

Any ideas!
 
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  #2  
Old 12-15-07, 04:35 PM
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There might have been moisture in the vac lines that froze. This is very common for big rigs and they gotta pour some antifreeze type fluid right in the lines.

If there was a problm with the booster, it would be a issue after warm up as well.
 
  #3  
Old 12-15-07, 05:11 PM
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the air sound is not abnormal. Sometimes it is quiet enough to miss but it is generally there.


When you push on the pedal, it allows air at atmospheric pressure to enter the rear of the booster (which makes the whooshing sound) which allows the vacuum on the front of the diaphram to pull it forward with gusto.

Since you did have vacuum, I would suggest the breather in the rear of the booster was sealed with ice. Once it warmed up and melted, you were good to go.

If you had a hole in the diaphram, it is often noticed as it causes excess air to enter the engine and makes it run lean or miss. Your brakes would also get no better regardless of temp.
 
  #4  
Old 12-15-07, 07:35 PM
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Nap
That does make sense
The breather freezing
I never had that before
How do I make it stop doing that?

Quite embarrassing
 
  #5  
Old 12-16-07, 06:30 AM
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No brake assist when started cold again

It is winter and cold again this morning
The same problem I had yesterday happened agian.
No power assist from the brake booster.
I got brakes manually and they feel fine.
Yesterday I unplugged the vacuum hose and check valve from the booster and there was lots of vacuum.
I did not do that today because I want to keep the car in the state it is in and dig up info for the tests I can do.
When the heater warms the inside of the car, the power assist will come back with loud air noise then the air noise will quit. Thats what happened yesterday.

So there is a power source on one end of the booster diaghram and there is a filter on the other end of the diaghram. Thats the facts as I know it.

I think I will go back out and press real hard on the pedal and that should break free the frozen diaghram that is not moving.
I think
 

Last edited by HotxxxxxxxOKC; 12-16-07 at 07:16 AM. Reason: Merged your thread. Try to keep all your posts in one thread.++
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