More C3 brake challenges.
Thread Starter
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
More C3 brake challenges.
I've just done a brake job and still have a somewhat spongy and low pedal:
--New SS calipers all the way around.
--New pads.
--New braided SS caliper lines.
--New (rebuilt) booster.
--New Bendix MC.
I bled the MC on the bench--must've taken 45 minutes--no bubbles anywhere and the piston got harder than a **** to push in after a while. I still have the bruise on my hand from the 3/8" ratchet extension I was using. Then the whole system was bled twice using a pressure bleeder and compressed air. (That works nice, BTW.) No fluid leaks anywhere and no bubbles from the bleeders. I have cycled 2 full quarts of Castrol LMA DOT 3/4 fluid through the thing. The pedal is hard when the engine's off.
Started the engine today and the pedal bled down--it's about 1/2" from the floor when it stops. Feels spongy. I haven't road tested it yet. For all I know it will stop better than new. The low pedal gives me concern, though.
Anything I'm overlooking? Or do I just bleed, bleed, bleed and bleed some more?
--New SS calipers all the way around.
--New pads.
--New braided SS caliper lines.
--New (rebuilt) booster.
--New Bendix MC.
I bled the MC on the bench--must've taken 45 minutes--no bubbles anywhere and the piston got harder than a **** to push in after a while. I still have the bruise on my hand from the 3/8" ratchet extension I was using. Then the whole system was bled twice using a pressure bleeder and compressed air. (That works nice, BTW.) No fluid leaks anywhere and no bubbles from the bleeders. I have cycled 2 full quarts of Castrol LMA DOT 3/4 fluid through the thing. The pedal is hard when the engine's off.
Started the engine today and the pedal bled down--it's about 1/2" from the floor when it stops. Feels spongy. I haven't road tested it yet. For all I know it will stop better than new. The low pedal gives me concern, though.
Anything I'm overlooking? Or do I just bleed, bleed, bleed and bleed some more?
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Re: More C3 brake challenges. (The Dude)
Had this problem with 3 (!) rebuilt boosters. Finally got a brand new GM booster, and that fixed it. Booster was $190 incl shipping at gmpartsdirect.com.
Drifting
Joined: Apr 2002
Posts: 1,743
Likes: 37
From: Stockton Ca
Re: More C3 brake challenges. (terry82)
I have SS lines and still get a low pedal. I think it is just part of 30 yr old brake design. I'm waiting for VB&P to make the kit to put C5 brakes on C3! Now that will be worth waiting for.
Racer
Joined: Oct 2001
Posts: 315
Likes: 0
From: West Orange New Jersey
Re: More C3 brake challenges. (The Dude)
I did stainless steele all around and still got mushy pedal from air coming in. Could not locate where the air was coming in from. Another forum suggested o-ring calipers that are air tight. This is my next step.
Instructor
Joined: Dec 2001
Posts: 139
Likes: 0
From: Kona Hi
Re: More C3 brake challenges. (The Dude)
I have exactly the same problem. Replaced all the same parts, bench bled m/c etc. Pushed almost a gallon of dot 3 through the system, no leaks or bubbles. Pedal goes soft as soon as I start it up. Got fed up and dropped it off at the vette guy this morning. Should know late today or tomorrow what he finds. From Zwede's post I'm figuring on the booster, but we'll see.
Drifting
Joined: Jan 2002
Posts: 1,484
Likes: 0
From: Northampton Ma
Re: More C3 brake challenges. (Chevyguy)
Mine was a bit spongy but it still stopped on a dime, bled everything again, pedal was firmer, but when you first hit the pedal it's still a little spongy for the first 1-2 inches, then perfect after that.
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Melting Slicks
Joined: Apr 2000
Posts: 3,341
Likes: 6
The best articles ever written on Vette disk brakes . . .
Go to forum member Terry Rudy's site --> http://www.corvettefaq.com
Go to the subsection on "Brake Systems".
Read the articles "Brake Service I" and "Brake Service II".
They are written by another forum member - Hib Halverson.
Go to forum member Terry Rudy's site --> http://www.corvettefaq.com
Go to the subsection on "Brake Systems".
Read the articles "Brake Service I" and "Brake Service II".
They are written by another forum member - Hib Halverson.
Thread Starter
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Re: (45ACP)
45ACP, great articles--very informative.
Chevyguy, let us know what a professional thinks. For all I know the car will stop on a dime. I haven't road tested it yet. But the pedal is spongy for an inch, inch and a half or so and then gets firmer.
Engine vacuum, BTW, is about 16" at idle in Park.
Chevyguy, let us know what a professional thinks. For all I know the car will stop on a dime. I haven't road tested it yet. But the pedal is spongy for an inch, inch and a half or so and then gets firmer.
Engine vacuum, BTW, is about 16" at idle in Park.