Brake booster causing high idle!!
Thread Starter
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Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
Brake booster causing high idle!!
I'm not sure if this question has been asked before or not... I haven't been able to search so here goes.
I just got my truck running after a rebuild. Whenever I apply my brakes the power booster does something and causes me to gain about 200-300 rpms. Then when I let off it goes back to normal idle. Anyone know whats up? Thanks!
I just got my truck running after a rebuild. Whenever I apply my brakes the power booster does something and causes me to gain about 200-300 rpms. Then when I let off it goes back to normal idle. Anyone know whats up? Thanks!
Thread Starter
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Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
I just replaced the valve with a brand new 90degree one from NAPA to replace my other non angled one. That's odd, I'll check it out though and let ya guys know tomarrow. Thanks for the help!
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Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
Ok, well I think I might know what the problem is. I took apart my Holley to rebuild it (another problem, lol) and I find that 2 big screws are missing out of the bottom of the carb. And they go straight through! So, my guess is that since those are open holes when I got my brakes it was sucking through there. I'll get some new Holley screws tomarrow if Checker has them in stock :-|, then try and see if it works...
Posting Guru
Joined: May 2003
Posts: 1,393
Likes: 0
From: Thomson, GA
That could also cause problems, but i think that your booster may still have been the culprit. Get everything back together and let us know. Wouldnt want to start throwing parts at it.
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Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
I went to a local shop here today and they said to leave the 2 two center screws out of the Holley because if they vibrate loose they will fall straight into the motor. So, I got that figured out but not the booster yet. I gotta work on my carb some more tonight and Saturday, but Sunday it'll all go back together so I can troubleshoot the booster problem.
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Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Ya know, I've heard of that fix but never have heard of it happening to anyone.
The booster is definitely on the way out. It will get worse and kill the motor when you step on the brakes. How's your master cylinder? Some places won't warranty their boosters without buying a new mc too.
Barry
The booster is definitely on the way out. It will get worse and kill the motor when you step on the brakes. How's your master cylinder? Some places won't warranty their boosters without buying a new mc too.
Barry
Thread Starter
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Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
BB, not sure on my master cylinder. It worked great until now 3 months ago when I pulled the motor. I had a rag stuffed in the hole, maybe some water got in and ruined it? Where do you get boosters?
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Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
BB, yes I've been loosing fluid, and the booster is all rusted on the outside. But it all seemed to work fine before I took out the motor. Is the booster supposed to make a hissing sound when the brakes are applied?
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
No it shouldn't, if it's a steady hissing then the diaphragm is leaking. Sounds like you need a new master and booster, they sell them together as a unit for a little cheaper then the individual parts.
Barry
Barry
Senior User
Joined: Jan 2003
Posts: 382
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From: Bonney Lake,WA USA
Mine hisses right when I step on the pedal but stops. I think that hiss is the air getting pulled in from the back of the booster. Nothing to do with the vaccum side (engine side). But ya, like Barry mentioned if it is hissing the whole time you are pressing the pedal then it is time to get a new unit.