C3 brakes won't bleed
Thread Starter
7th Gear
Joined: May 2013
Posts: 7
Likes: 0
C3 brakes won't bleed
I recently rebuilt the front end on my car and replaced the brake lines. I decided to bleed all four brakes. Tried the two man system, one pumping while the other bleeds. No fluid comes out. Tried vacuum, no fluid comes out. During the bleeding process I had the cover of the MC on. I did crack open the outlet lines on the MC and fluid came out. Still could not bleed brake lines. Decided to drain the system. The only way I new how was to take all the fluid out of the MC. Opened the bleeders and blew air through the system. Was this wrong? Air and fluid came out. The fluid looked prity bad. I am still unable to get fluid to come out of the bleeders. Filled the MC and left the bleeders open to see if it would gravity feed. Still nothing. Help me, Help me, I'm losing my mind.
Le Mans Master
Joined: Mar 2001
Posts: 5,738
Likes: 644
From: Lincoln, CA
When you applied vacuum to a bleeder to did the gauge move or just hold steady?
Many times when doing a complete change a big air pocket will prevent the brake pedal from moving any fluid. Close all but one bleeder and with a vacuum setup so if you can pull air though the line.
But the best and fastest way to do it is with a Motive brake bleeder.
Many times when doing a complete change a big air pocket will prevent the brake pedal from moving any fluid. Close all but one bleeder and with a vacuum setup so if you can pull air though the line.
But the best and fastest way to do it is with a Motive brake bleeder.
Race Director
Joined: May 2006
Posts: 18,737
Likes: 2,583
Drifting
Joined: Aug 2005
Posts: 1,372
Likes: 4
From: Springfield VA
I just bleed my entire system that was dry. Rebuilt all 4 calipers, replaced 4 hoses, 2 brake lines, and the rotors.
I got some clear hose from lowes, 20 foot of 5/16 I think, and attached to the bleeders. I ran the hose about 3 foot higher than the MC. Opened the valves and let gravity push some fluid out of most. Then I lightly pressed the brake pedal and held it. This pushed the fluid and air out but the air floats to the top of the hose. Then let off the peddle and it sucks the fluid back in.
No air and perfect pedal.
I use to do this when I was a mechanic when I had to do a lot of brake work or the car was being hard to bleed. Also able to do this with no other help, 1 man bleed.
I got some clear hose from lowes, 20 foot of 5/16 I think, and attached to the bleeders. I ran the hose about 3 foot higher than the MC. Opened the valves and let gravity push some fluid out of most. Then I lightly pressed the brake pedal and held it. This pushed the fluid and air out but the air floats to the top of the hose. Then let off the peddle and it sucks the fluid back in.
No air and perfect pedal.
I use to do this when I was a mechanic when I had to do a lot of brake work or the car was being hard to bleed. Also able to do this with no other help, 1 man bleed.
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
When we did dad's car we started with everything new but the hard lines and we just installed it all and filled the master and cracked the bleeders. When fluid started coming out of the bleeders then we bled it a bit more. No bench bleeding of the master.
The hoses running up higher than the master sounds like a cool trick if you don't want to do any flushing. Otherwise, run a hose into a bottle with a little fluid in it and pump the brakes. The air can get out but only fluid can get back in.
The hoses running up higher than the master sounds like a cool trick if you don't want to do any flushing. Otherwise, run a hose into a bottle with a little fluid in it and pump the brakes. The air can get out but only fluid can get back in.
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Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Gravity bleed is about the only method I can make work on my old Vettes. It's best done while you're working on something else in the garage so you can monitor the fluid level in the master. It's effective, it's easy but takes a while. Any method that requires working the pedal, I could never make work. It seems to 'scatter' the air in the dual-piston calipers.
Good luck!
Good luck!
Last edited by 73, Dark Blue 454; Sep 30, 2013 at 09:05 PM.
Drifting
Joined: Mar 1999
Posts: 1,432
Likes: 22
From: Oxford CT
Gravity bleed is about the only method I can make work on my old Vettes. It's best done while you're working on something else in the garage so you can monitor the fluid level in the master. It's effective, it's easy but takes a while. Any method that requires working the pedal, I could never make work. It seems to 'scatter' the air in the dual-piston calipers.
Good luck!
Good luck!
Racer
Joined: Aug 2013
Posts: 264
Likes: 58
From: Virginia
If your master cylinder went dry and you got some air in there, It will take some time to get it all out. Little air bubbles get hung up at every fitting and every bend along the way. With all the bleeders closed and reservoir filled, and a small hammer, GENTLY tap on each caliper, hose fitting, line fitting, etc. all the way back to the MC.
Then start the whole bleed sequence again, BUT start at the fittings at the MC. Then EVERY fitting along the way to each bleeder.
Having a helper makes it a little easier. I just did this whole process when I replaced my MC. I used a vacuum pump just like ddawson's photo above and spent an entire afternoon and into the dark until it was right. Took her out for a test drive and still had a low, somewhat soft pedal. The next morning I attacked it again, the old fashioned way, with my neighbor pumping the pedal. After one bleed at each caliper, it was just right.
Then start the whole bleed sequence again, BUT start at the fittings at the MC. Then EVERY fitting along the way to each bleeder.
Having a helper makes it a little easier. I just did this whole process when I replaced my MC. I used a vacuum pump just like ddawson's photo above and spent an entire afternoon and into the dark until it was right. Took her out for a test drive and still had a low, somewhat soft pedal. The next morning I attacked it again, the old fashioned way, with my neighbor pumping the pedal. After one bleed at each caliper, it was just right.
Pro
Joined: Oct 2009
Posts: 523
Likes: 4
From: Calgary Alberta
I used the system below and everything worked great with a Wilwood MC and Wilwood D8-4 calipers.
http://www.speedibleed.com/
http://www.speedibleed.com/
6th Gear
Joined: Sep 2015
Posts: 6
Likes: 1
From: Boaz Alabama
I am having this same problem. Replaced rear calibers and pads. Started to bleed brakes ,as I always have , 2 people. Pump and hold. Started to work then ran m/c rear half went dry. Now no fluid will come out.. Help. I have read herE on re-centering the proportion valve. The thread says to step on the brake pedal several times. Then bleed the front and rear caliber simountanious how do you bleed front and rear at the same time. I can't be in two places at the same time..I just do not understand this system. I have never worked on or own a 1968 corvette before.i have worked on VW and other cars for 40 years so I do know how brakes work and how to bleed there systems. This system with a proportion valve makes no sense to me. If the system is made to block off the rear or front in the event of a failure in front or rear them why do I have NO pedal now? It look like the system works backwards or what it is suppose to. Please explain what to do to center the valve and then bleed the brakes.
Burning Brakes
Joined: Mar 2006
Posts: 829
Likes: 131
From: Spartanburg SC
Before I would go after the mc, I would disconnect the brake lines at the rear calipers and see if you can get fluid thru the lines. That would narrow down the issue to the calipers. I guess there could blockage in the caliper from machining , tho I personally have never seen that. I also have never had an issue with the proportioning valve.
Le Mans Master
Joined: Mar 2001
Posts: 5,738
Likes: 644
From: Lincoln, CA
If the MC went dry I would bench bleed it again.
What I have run into a few times with replacing calipers on car is the pedal throw is not long enough to push enough fluid.
Kind of like moving water though a straw. Sip for a short time and water just goes back down.
I now either use pressure or vacuum to get enough moment instead of relaying on the brake pedal.
What I have run into a few times with replacing calipers on car is the pedal throw is not long enough to push enough fluid.
Kind of like moving water though a straw. Sip for a short time and water just goes back down.
I now either use pressure or vacuum to get enough moment instead of relaying on the brake pedal.
6th Gear
Joined: Sep 2015
Posts: 6
Likes: 1
From: Boaz Alabama
Got brakes fix. Here is what I did.
I went and bought a pressure pump bleeder. Although I was pulling air(everyone said this would happen I don't know how to stop the air coming in around the bleed screw) I pulled enough fluid to make pedal bleeding work. Thanks for all the info.
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
Put some grease on the screw so it blocks the air coming in around the threads.