Brake Bleeding...
Thread Starter
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
Brake Bleeding...
I am trying to bleed the front calipers on my 81, not having any luck. Some history first: Removed the calipers many months ago to have them powder coated. They have been sitting on the shelf since. The calipers were all rebuilt befor installing them, including new bleeder valves. So today I start in the back and both back calipers bled fine.
Go to the front and all I can get is NOTHING! I have a hand held vacuum pump but I can't use it because the vacuum leaks through the threads on the bleeder valve. If I shove the vacuum hose up and over the whole bleeder I can pull fluid through it but when I take the hose off the tighten the bleeder I loose the fluid and it will only pump a little fluid through when I loosen up the bleeder and my wife pushes the pedal down slow. The secone time she pushes the pedal there is no more fluis coming out. We must have done this 20 times today and finally gave up.
The rear is finebecause I never took them off the car and have no intention of doing so now! The heck with powder coating. Any ideas? All new parts including hoses.
Go to the front and all I can get is NOTHING! I have a hand held vacuum pump but I can't use it because the vacuum leaks through the threads on the bleeder valve. If I shove the vacuum hose up and over the whole bleeder I can pull fluid through it but when I take the hose off the tighten the bleeder I loose the fluid and it will only pump a little fluid through when I loosen up the bleeder and my wife pushes the pedal down slow. The secone time she pushes the pedal there is no more fluis coming out. We must have done this 20 times today and finally gave up.
The rear is finebecause I never took them off the car and have no intention of doing so now! The heck with powder coating. Any ideas? All new parts including hoses.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
When you removed the front calipers, is there a chance that all the fluid was drained from the front reservoir of the master cylinder. If so; you will need to remove the master cylinder and bench bleed to ensure all the air is removed from the master cylinder.
When you bled the rears with no pressure to the fronts you may have shifted the proportioning valve. This would be confirmed by the brake warning light being illuminated on the dash.
Do as Roger says and gravity feed the fronts; ensuring that the reservoir doesn't get low enough to re-introduce air back into the actuating portion of the master cylinder.
If the warning light is still on a serious brake application is required to re-center the proportioning valve.
When you bled the rears with no pressure to the fronts you may have shifted the proportioning valve. This would be confirmed by the brake warning light being illuminated on the dash.
Do as Roger says and gravity feed the fronts; ensuring that the reservoir doesn't get low enough to re-introduce air back into the actuating portion of the master cylinder.
If the warning light is still on a serious brake application is required to re-center the proportioning valve.
Thread Starter
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
Thread Starter
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
When you removed the front calipers, is there a chance that all the fluid was drained from the front reservoir of the master cylinder. If so; you will need to remove the master cylinder and bench bleed to ensure all the air is removed from the master cylinder.
When you bled the rears with no pressure to the fronts you may have shifted the proportioning valve. This would be confirmed by the brake warning light being illuminated on the dash.
Do as Roger says and gravity feed the fronts; ensuring that the reservoir doesn't get low enough to re-introduce air back into the actuating portion of the master cylinder.
If the warning light is still on a serious brake application is required to re-center the proportioning valve.
When you bled the rears with no pressure to the fronts you may have shifted the proportioning valve. This would be confirmed by the brake warning light being illuminated on the dash.
Do as Roger says and gravity feed the fronts; ensuring that the reservoir doesn't get low enough to re-introduce air back into the actuating portion of the master cylinder.
If the warning light is still on a serious brake application is required to re-center the proportioning valve.
Instructor
Joined: May 2010
Posts: 113
Likes: 0
From: Shelby Twp. Michigan
I just went threw this Thursday! Before ya light it on fire walk away.LOL! Crack the bleeders open just a bit and come back in the morning and close em. That's how I did mine. I tried my Mighty vac, my wife pumped em for ever and nothing. Gravity bled em over night and bingo! I did have my wife pump them just to make sure the following day.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Then I go to the RF and do the same and usually all the air comes out.
However if the master still has air inside of it your pedal will be low.
The master cylinder must have a really good bench bleed done on it or your going to have trouble. I always use the tubes and I bleed until there is absolutely no more air visible. To me the final spot to look for air is the little hole in the bottom of the rear cylinder. If there is air in that little hole it must be forced out. Good Luck
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Thread Starter
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
Yes. I usually start with the LF and as its dripping I tap all joints and unions and lines just to try and help dislodge any air that is stuck in threads and etc.
Then I go to the RF and do the same and usually all the air comes out.
However if the master still has air inside of it your pedal will be low.
The master cylinder must have a really good bench bleed done on it or your going to have trouble. I always use the tubes and I bleed until there is absolutely no more air visible. To me the final spot to look for air is the little hole in the bottom of the rear cylinder. If there is air in that little hole it must be forced out. Good Luck
Then I go to the RF and do the same and usually all the air comes out.
However if the master still has air inside of it your pedal will be low.
The master cylinder must have a really good bench bleed done on it or your going to have trouble. I always use the tubes and I bleed until there is absolutely no more air visible. To me the final spot to look for air is the little hole in the bottom of the rear cylinder. If there is air in that little hole it must be forced out. Good Luck
Thanks again. I am going to bench bleed the master cylinder then I will gravity bleed the front. I am sure this will solve my problem. Really, thanks for all your help. This is the last thing I need to fix then I will be able to get the car inspected and drive it for the first time in 4 years! By the time I am ready it will be winter and it will be be putting the car away.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
Dannyman, do I need the have the engine running to check the warning light or just the key to the acc position? Also, if the warning ligjht is still on what do you mean by a serious application, slam on the brakes? Thanks for your help, I drove myself crazy today with this problem now I know what to do. You and Roger are the best! Enjoy the rest of your weekend, I will now.
You will want to gravity bleed first and ensure the system is full of fluid. If the warning light is illuminated then the proportioning valve has been shifted internally because of the initial pressure differential between the front and rear systems. The hard application (either steady hard, or slam) is needed to re-center the valve and extinguish the light.
Thread Starter
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
Ropger, Dannyman & PowdercoatBill,
Thank you all very much, I now have brakes. It was what you all said, I needed to bench bleed the master cylinder. I hope you all have a great week.
Thank you all very much, I now have brakes. It was what you all said, I needed to bench bleed the master cylinder.
I hope you all have a great week.
