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How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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tiresharkdb
New User
Aug 19, 2012, 11:05 AM
Post #1 of 7
(13456 views)
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How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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Ok, a mechanic told my dad his brake booster went out a while back. I ordered a used one online, and installed it myself. Replaced it and everything worked fine. 3 months later, and the problem has returned.
The part is under warranty, but they want a mechanic to make sure it isn't a vacuum leak, instead of the booster, before they will take it back.
What i want to know is how i can isolate the brake booster and the vacuum system to troubleshoot.
The brake is very firm, and makes a whooshing noise when i push on it. If i 'lightly' place my foot on the brake (while engine is running) and hold it there, it will make a constant low wwhhhsssssss and the engine rpms will raise by about 200. When i remove the brake pressure, the engine drops to normal idle.
With the engine off, i pump the brakes to get rid of the vacuum built up. i hold the brakes down and start engine... normally the brake should lower and relax a little bit, when the engine starts... but it doesnt do that... it stays where i have it, and the whooshing noise is constant.
I ran the engine for a few minutes to build up a vacuum, then shut it off. I waited 2 minutes and then removed the check valve from the booster -- it made a loud PPSSHHT sound as the air rushed in. someone said that means its holding a vacuum... not sure if that is correct or not.
The booster only has 1 hose that connects to the manifold. I checked the one-way valve and it is working properly. When i remove the hose with the engine running, and place my finger over it, it has lots of suction.
im not 100% sure about how this all works... but wouldn't a vacuum leak be between the manifold and the booster... somewhere along that hose or at the connections? if there is no leak out there, then it must be inside the booster... right?
should i do the 'spray carb cleaner around the manifold' thing to check for a vacuum leak at the manifold? or have i done something above that tells you the problem is with the booster?
Thanks for any help!!
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 19, 2012, 12:43 PM
Post #2 of 7
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Re: How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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It worked for three months so chances are it wasn't an installation problem so my guess in another bad booster. Used is used,
T
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nickwarner
Veteran
/ Moderator
Aug 19, 2012, 4:00 PM
Post #3 of 7
(13396 views)
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Re: How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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You could pinch off the hose and then hit the brake pedal. If your idle holds still you know its the booster. I would recommend not ever buying used brake parts. The wrecks at the boneyard didn't stop on a dime or they wouldn't be wrecked. Brake parts are too important to use anything less than new every time. Anything less and you can risk the lives of others who share the road with you and that isn't fair to them.
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tiresharkdb
New User
Aug 19, 2012, 7:15 PM
Post #4 of 7
(13388 views)
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Re: How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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Thanks guys. Yeah... i started not to go used on this part... especially since the used part was the same age/mileage as the one that went out (10 yrs, 100k miles) -- wont make that mistake again, heh. I'm lucky it went out within the warranty.
Hey when i was removing the booster, i heard something metal fall off as i was trying to wiggle the booster out from behind the master cylinder. I'm 'pretty' sure it was this piece:
and im 'pretty' sure it goes in the middle of the booster, where the master cylinder butts up against it. It doesnt screw in or anything, it just slides down into the hole like so:
Can someone confirm that is where that goes... what is the function of that piece?
Does it affect the function of the booster?
Thanks again! 
(This post was edited by tiresharkdb on Aug 19, 2012, 7:48 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 20, 2012, 4:53 AM
Post #5 of 7
(13371 views)
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Re: How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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That's pushing (pushrod) from the booster to the master cylinder and needs to be just right. I can't say from experience on this one if that should be stuck in place or just held by it all being assembled. Some of those things are adjustable for correct operation or preset or adjusted elsewhere as needed if ever needed.
How long should a booster last? Who knows? For some reason here in a rust belt these seem to last till a whole vehicle falls apart (not funny) but it's a moving part with rubber so age should be a factor.
What is the oil like stain in the pics? If brake fluid that wasn't spilled or a solvent to remove nuts then master may be leaking out back of itself to add to this fix.
Used brake parts are a no-no. A bracket somewhere perhaps or a core to rebuild would be OK but not for this as I can't think of anything that isn't available new,
T
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tiresharkdb
New User
Aug 21, 2012, 4:04 PM
Post #6 of 7
(13341 views)
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Re: How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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Thanks tom.
I did the 'brake cleaner' check for a leak before i removed it, and nothing showed up.
I actually had another truck same model/year that i had been working on, and just to be sure, i put this booster in the other truck to see if it would work... the problem occurred on the other truck as well... so that confirms 100% that it's the booster.
thx again!
p.s. - i suppose i should recommend the ebay seller: chuckandeddies -- they have tons of parts and offer a 6 month warranty on used items... you usually dont find used part warranties that last longer than a month or two.
(This post was edited by tiresharkdb on Aug 21, 2012, 4:06 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 22, 2012, 12:00 AM
Post #7 of 7
(13328 views)
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Re: How to troubleshoot bad brake booster (96 chevy c1500 V6)?
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OK - Good luck with the fix. Just a note on brake cleaner -- it is NOT rubber friendly so watch out for that and what you use it on,
T
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