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1971 Chevy Truck brakes slow to stop
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xprmntl1
Novice
Aug 5, 2011, 2:20 PM
Post #1 of 10
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1971 Chevy Truck brakes slow to stop
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1971
Chevy Truck
4x4
350C.I.
199,999
I have replaced: Master Cylinder, front brake pads(disc), booster valve, all new brake lines front to back even rubber lines to calipers.
Differentials are from a 1991 Suburban 4wd, using prop. valve and booster from my 4wd 1971.
I have a very firm pedal, have to use excessive force to get truck to stop, cant get brakes to lockup on grass or gravel, not sure if booster is my problem. I pulled vacuum hose loose from booster while truck is running and rpm's dont drop, but if I block off hose with my finger rpm's drop. Could my booster have an internal leak? I changed the blockoff valve that mountes to front of booster also.
Thanks!
(This post was edited by xprmntl1 on Aug 5, 2011, 2:21 PM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Aug 5, 2011, 3:14 PM
Post #2 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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Shut the truck off, pump the brake pedal a couple times to exhaust all vacuum. Now hold firm pressure on the brake pedal while starting the truck and watch for the pedal to drop. If it does, the booster is working.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Aug 5, 2011, 3:33 PM
Post #3 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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Check the booster is getting full intake manifold vacuum and what the real intake manifold vacuum is.
Other maybe: There's a proportioning valve that may be involved?
T
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xprmntl1
Novice
Aug 5, 2011, 3:41 PM
Post #4 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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Ok, I did as you said and the pedal most definitely did not drop at all. So the booster is the problem? Also, with the booster not working properly or at all will I not be able to lock the brakes up with enough force? Thanks.
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xprmntl1
Novice
Aug 5, 2011, 3:42 PM
Post #5 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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I'm not sure what full vacuum is, but if I cover the hose with my finger it has pretty good suction? I was going to replace the prop. valve next, just didnt wanna keep throwing parts at this problem. Thanks!
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Hammer Time
Ultimate Carjunky
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Aug 5, 2011, 3:43 PM
Post #6 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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Yes, that is the whole purpose of the booster. It increases the brake pressure.
Make sure you have a good vacuum supply going to it from direct manifold vacuum.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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xprmntl1
Novice
Aug 5, 2011, 3:46 PM
Post #7 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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Do trucks with discs and no power brake booster have the same feel as mine?
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Hammer Time
Ultimate Carjunky
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Aug 5, 2011, 4:05 PM
Post #8 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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I don't know. I've never seen a truck with Disc brakes and no power in the last 30 years.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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xprmntl1
Novice
Aug 5, 2011, 7:20 PM
Post #9 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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Thanks for your help guys 
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Tom Greenleaf
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Aug 5, 2011, 9:50 PM
Post #10 of 10
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Re: 1971 Chevy Truck brakes slow to stop
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Quote">>Do trucks with discs and no power brake booster have the same feel as mine?<<"
No. Vehicles without power assisted brakes or steering used to just increase the leverage for brakes and steering wheels were larger with more turns stop to stop of the wheel. They drove fine but a pain - had a few. I don't think much of anything short of a lawn tractor doesn't do power assist anymore for a long time now,
T
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