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Help! Bled brakes till my legs seized!

PeterF

Member
Joined
Oct 22, 2011
Messages
20
Location
Queensland, Australia
My 79 had brake pedal to the floor, so my son and i investigated and found leaking rear calipers. So we installed new calipers, pads and rotors (as they were very worn) today. All great. Then we bled them, and bled and bled. We used over a litre of fluid. For hours. We could get firmness to the pedal during pumping, but when the engine is on, pedal straight to the floor. What is happening!? Thanks Peter in Queensland Australia.
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
The following suggestions will work if you DID NOT drain the system of brake fluid while you had the calipers off.

First thing I'd do is make sure there are no leaks in the system.

Next, I'd verify that the master brake cylinder is in good condition. This may include unbolting the master and moving it forward so you can inspect the cavity between the master and the brake booster to verify the master is not leaking.

Thirdly, purchase or borrow a pressure bleeder, install it and bleed the system using that. Begin by raising the back of the car with jack stands and removing the rear wheels. Bleed the master cylinder first. Then do both bleeders in the right rear caliper. You likely are going to get a lot of air out of the right rear but bleed it until there are no bubbles. When you get to the point there are no bubbles in the hose, do one more opening of the bleeder while tapping the caliper with a plastic or rubber hammer to dislodge any additional air bubbles. Next do both bleeders in the left rear. Move to the right front and bleed it finish with the left front.

Now...if you drained the system dry by mistake when you had the calipers off, you may need to bench-bleed the master cylinder which requires it be removed. Once you do that, then follow the procedures above.

Let us know how things go.
 

PeterF

Member
Joined
Oct 22, 2011
Messages
20
Location
Queensland, Australia
[QUOTE

Let us know how things go.[/QUOTE]

Thanks very much for the detailed procedure. We'll go through that next Saturday. The brake bleeder will be a good tool to have. Ill let you know how we go!!
 

LLC5

Well-known member
Joined
Sep 28, 2004
Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
My 79 had brake pedal to the floor, so my son and i investigated and found leaking rear calipers. So we installed new calipers, pads and rotors (as they were very worn) today. All great. Then we bled them, and bled and bled. We used over a litre of fluid. For hours. We could get firmness to the pedal during pumping, but when the engine is on, pedal straight to the floor. What is happening!? Thanks Peter in Queensland Australia.



A lot of times when pushing an old master cylinder to the floor to bleed it, the seals will be damaged internally.

When bleeding a system with an old master cylinder on it, it is always advised to not push past the normal pedal travel.
 

GTR1999

Well-known member
Joined
Sep 4, 2003
Messages
1,146
Location
New Haven CT
Corvette
1969,1972,1975
The guys gave you some very good advice. I would suspect the MC too and would pull it to see if it's leaking or replace it. Now you're about as far away as you can get but should be able to get the parts. I have a few of my units in Australia but they take time to get there.

I like to use the Motive bleeders now. They are basically a garden sprayer with gauge but work great. I like to pump them up to about 12-13 psi and watch the guage, it should stay where you pump it to. If it creeps down you have a leak someplace. You check each circuit, front & rear, separately.

Check the rotor runout as well- I set mine to 0-003" max runout thru 360*, you can get by with 005" but the closer to -0- the better. Also if you replaced the fronts, you have to replace the copper washers on the hose end or they will leak.
 

PeterF

Member
Joined
Oct 22, 2011
Messages
20
Location
Queensland, Australia
Thanks GTR, i am thinking it will be worth replacing the master cylinder, the state of the calipers corrosion wise they were terrible. The car has been sitting alot too. Those kind of parts available here.

Ive been looking at those weed sprayer type bleeders, what are the vacuum hand pump ones like? I have not found any of the pressure ones locally yet, but ill keep looking. Unfortunately i dont own a compressor, which would be the best way to go i suppose, peter
 

Antz81

Well-known member
Joined
Dec 21, 2013
Messages
936
Location
Auckland, New Zealand
Corvette
1981 4 speed
Ive been looking at those weed sprayer type bleeders, what are the vacuum hand pump ones like? I have not found any of the pressure ones locally yet, but ill keep looking. Unfortunately i dont own a compressor, which would be the best way to go i suppose, peter

Vacuum type bleeders won't work on c3s.
 

PeterF

Member
Joined
Oct 22, 2011
Messages
20
Location
Queensland, Australia
Still at it

We got a new master cylinder, bled it, but we are still getting heaps of air. We have a leak somewhere. Arrghh!
 

PeterF

Member
Joined
Oct 22, 2011
Messages
20
Location
Queensland, Australia
Success!

BRAKES ARE BLED AT LAST. There was a video on YouTube that exactly described my difficulty. The proprtioning valve was limiting the flow to the rear brakes (as it was designed to do) when a system failure occurs. You cant bleed until you have reset the valve. Following the youtube instructions, we reset the rod inside by pushing it with a very small screwdriver. The proof it worked was the brake warning light now came off after starting, when it stayed on before. Once the rod was pushed back the braked bled normally, with no hassle. We have pedal again! Whether i needed a new master or not dont know but i at least have very clean lines! That video Why Your Old Chevy's Brakes Won't Bleed. - YouTube
 

bill81vette

Moderator
Joined
Jan 17, 2004
Messages
4,316
Location
Troy,NY
Corvette
1981 dark blue metallic
great news,enjoy!!!!:thumb:thumb
 

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