Topic: Difficult stopping vette.
in Forum: C3 Q&A with Dave McLellan
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This past spring when I got my 76 vette out of storage I noticed that the car would barely slow down and pull to one side when the brakes were applied. When I got home to my garage the wheels were pulled and I found that the front brake calipers had leaked.
Having no time to work on the brakes I took it to the GM dealer who specializes in vettes. Installed were new front calipers, new rotors, new pads, new braided steel brake lines.
New steel lines replaced in the rear also. Synthetic brake fluid is used because i understand it's less likely to absorb water. the vette is stored 5 months of the year.
The vette doesn't pull but it won't come to a quick stop. The pedal does go almost to the floor but it doesn't feel mushy (owned this vehicle for over 10 years and i never remember having much pedal). Also, braking isn't to good until the system gets nice and warm; could the synthetic fluid cause this?
All other brake componets are original (36 years old). Should I be looking at a new master cylinder, booster, proportining value, or all 3?
Ideas, suggestions...
thanks
john
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
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#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
I would first flush the synthetic fluid out of the system completely, and replace it with good old regular DOT 4 fluid, bleed the system really well, and then drive with no problems. But then, it ain't my car.
Two things have most likely taken place...one...the dealer didn't get the system bled properly, and two, synthetic fluid(DOT 5) WILL give you a lower, and mooshy pedal...it will compress some, unlike regular brake fluid. SO, add the compressablilty of the fluid, and some air in the system, and you get very little actual braking.
Or, you could just have the system bled again, and see if that helps any...it may just simply have too much air in it.
Two things have most likely taken place...one...the dealer didn't get the system bled properly, and two, synthetic fluid(DOT 5) WILL give you a lower, and mooshy pedal...it will compress some, unlike regular brake fluid. SO, add the compressablilty of the fluid, and some air in the system, and you get very little actual braking.
Or, you could just have the system bled again, and see if that helps any...it may just simply have too much air in it.
Joel Adams
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Lifetime MemberTemple City, CA - USA
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Vette(s): 1969 Daytona Yellow. 350 / Automatic.
I'd take it right back to that dealer and tell them it doesn't stop right after all the work they did. They should have road tested it anyway. Seems like they didn't.
Some good points. I'll get the fluid flushed and then refill with non-synthetic. This sounds like the logical first step before I go replacing part.
thanks
thanks
could be they never got the proportioning valve set and you just have rear brakes it can take a couple of tries to get it set. if this was the case and the circuit works the brake light would be on to let you know.
Lifetime MemberEquinunk, PA - USA
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Vette(s): 1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.
I think the master cylinder deserves a good look, AFTER all the things said previous to this post.
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Frederick, MD - USA
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Vette(s): 1969 convertible L71 427/435 4-speed black interior
I agree with the synthetic brake fluid being a likely suspect. If the dealer installed it without thoroughly flushing the old fluid out of the system and thoroughly and completely bleeding it of air you'll have problems. Synthetic fluid is incompatible with DOT 3 or 4 brake fluid. It will create a milky mess and make for stopping problems due to being nearly impossible to bleed all the air out.
Most, if not all modern performance cars specify that synthetic brake fluids not be used. In hard handling the fluid can form bubbles and reduce braking effectiveness.
I'm not saying synthetic brake fluid is necessarily a bad thing...many have used it for years without issue. I'm just saying it's not for every application and it does have compatibility issues.
I'm having the mushy pedal problem also, which was "normal" until a month ago, when it went to the floor. I took it to my mechanic (yeah, I don't work on mine any more, sorry), and he's replaced the master cylinder THREE times, new proportioning valve, broke some lines and replaced them, too. Full bleed.
I had GREAT pedal when I picked it up (all three times!), then within two days it fades back to the floor. Pumping them WILL stop the car, but we can't seem to chase down why this keep happening. Frustrating! 
Any advice? Before I take a match to it ...
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
1: Rotors are warped
2: Wheel/hub bearings are loose
3: See #1
2: Wheel/hub bearings are loose
3: See #1
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Lifetime MemberTemple City, CA - USA
Joined: 10/3/2010
Posts: 365
Vette(s): 1969 Daytona Yellow. 350 / Automatic.
Joel, doesn't this sound like the old-style caliper seals are sucking in air? Seems I read that when I did mine but geez, that was 2 months ago.
in Forum: C3 Q&A with Dave McLellan
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