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How to tell if brake booster is bad - and how to replace!


6 replies to this topic

#1 wambus

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Posted February 3, 2013 at 03:30 pm

I have 99 Grand Caravan.  I apologize for not searching for an answer, but the search function here seems to be producing odd results.

 

I have been fighting with a brake problem for a couple of years now; I have posted about this before.  Today I took another look at the rear drums.  It appears that the one remaining from when the van was new was seized up.  I already had planned on replacing it, so that it fixed. 

 

Now, I have been told that the brake booster is bad.  The symptoms are primarily grabby brakes on the first push, an sometimes hard brakes (so my wife says).  I was talking to a guy at the parts store and he asked me if the brakes make a Woosh sound when the pedal is pushed.  I staed that yes, they did,  He told me the booster is bad.  Is this true?  Are there other possible things to check?  If it is bad, how the heck do I get it out of the engine bay?  Looks as though the intake must come off.....



#2 ImperialCrown

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Posted February 3, 2013 at 03:44 pm

A 'whoosh' while holding the pedal down would be a vacuum leak from a torn internal diaphragm.  The booster would need replacement. 

If the master cylinder is leaking brake fluid out the rear cup into the booster, the cylinder would be needing replacement as well.

The 'wiper bucket' can be removed to open up a whole lot more room to get at things in the engine compartment.



#3 valiant67

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Posted February 3, 2013 at 04:29 pm

I concur, and IC is right about the master cylinder leak possibly being the cause of the booster failure.

#4 bguy

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Posted February 3, 2013 at 05:11 pm

If your booster is holding vacuum you should have a "regular" brake feel for at least one brake application with the motor off.  In other words if you were rolling down your driveway before you start the engine it should feel normal as you depress the brake. A second or more pump would deliver that stiff unassisted feel. Not holding vacuum would indicate a leaking diaphragm or a faulty check valve. The other possibility if the booster is good is a weak vacuum signal from the manifold. It may be related to the drivability symptom in your other thread.



#5 wambus

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Posted February 3, 2013 at 05:44 pm

Outstanding response time! 

 

I replaced the master cylinder last year trying to firm up the brake pedal.  The original cylinder was not leaking. 

 


There is one vacum line to the booster, yes?  Is there a way to check the fitting and line for being sealed?  A new booster is only $73.00, but hey - that's $73.00 I could spend on some other broken stuff....



#6 chuzz

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Posted February 3, 2013 at 08:27 pm

I've always used the pedal to check. If you put your foot on the brake pedal and start the van, what happens? If it moves slowly towards the floor when you start the van, that's normal. If it feels hard or doesn't move, the booster is probably bad.



#7 A.j. Schreiber

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Posted February 4, 2013 at 05:13 pm

I've always used the pedal to check. If you put your foot on the brake pedal and start the van, what happens? If it moves slowly towards the floor when you start the van, that's normal. If it feels hard or doesn't move, the booster is probably bad.

+1 I'd try that




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