Brake Problem - I Need Help!!!
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
Brake Problem - I Need Help!!!
On my 69' I've just replaced the front to rear rigid brake line (a little hole in the old one
). Stainless steel braided brake hoses added too...
The problem is that now there is no oil at rear calipers so I can't bleed the rear system (no problem with front calipers
).
All the lines are ok (checked with compressed air) and apparently there's no problem but oil is not able to arrive at the left rear brake line block too!!
I've also tried to replace the master cylinder (with another one which surely works) but it's the same
I've used this push rod settings :
Could be the proportioning valve (damaged or not well regulated)????
It's really a proportioning valve (tunable) or only a brake line distribution block (not tunable)?
That looks like mine, but it has also an electric wire attached to the central pin...
). Stainless steel braided brake hoses added too...The problem is that now there is no oil at rear calipers so I can't bleed the rear system (no problem with front calipers
).All the lines are ok (checked with compressed air) and apparently there's no problem but oil is not able to arrive at the left rear brake line block too!!
I've also tried to replace the master cylinder (with another one which surely works) but it's the same
I've used this push rod settings :
Could be the proportioning valve (damaged or not well regulated)????
It's really a proportioning valve (tunable) or only a brake line distribution block (not tunable)?
That looks like mine, but it has also an electric wire attached to the central pin...
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Have you tried to blow air from the rear caliper thru the MC with everything connected up? If you get air you should get fluid. Its stuborn sometimes. Might help to get a mighty vac or a power bleeder
On my 69' I've just replaced the front to rear rigid brake line (a little hole in the old one ). Stainless steel braided brake hoses added too...
The problem is that now there is no oil at rear calipers so I can't bleed the rear system (no problem with front calipers ).
All the lines are ok (checked with compressed air) and apparently there's no problem but oil is not able to arrive at the left rear brake line block too!!
I've also tried to replace the master cylinder (with another one which surely works) but it's the same
I've used this push rod settings :
Could be the proportioning valve (damaged or not well regulated)????
It's really a proportioning valve (tunable) or only a brake line distribution block (not tunable)?
That looks like mine, but it has also an electric wire attached to the central pin...
). Stainless steel braided brake hoses added too...The problem is that now there is no oil at rear calipers so I can't bleed the rear system (no problem with front calipers
).All the lines are ok (checked with compressed air) and apparently there's no problem but oil is not able to arrive at the left rear brake line block too!!
I've also tried to replace the master cylinder (with another one which surely works) but it's the same
I've used this push rod settings :
Could be the proportioning valve (damaged or not well regulated)????
It's really a proportioning valve (tunable) or only a brake line distribution block (not tunable)?
That looks like mine, but it has also an electric wire attached to the central pin...
8th Gear
Joined: Jul 2007
Posts: 8
Likes: 0
From: White River Jct., Vermont
if the proportioning valve was activated through the process of how you bled your brakes, it may need to be reset. the pin and wire activate your dash brake warn light to let you know the valve has been activated and that you need to check your brakes for leaks. example, if the front line(s) fail pressure from the rear lines push a plunger in the prop valve to seal off the front from the MC and also pushes on the switch that is screwed in there to turn on your brake light in the dash. same thing happens if the rear line(s) fail.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
Proportioning valve, distribution valve, brake warning valve, whatever! The valve has numerous different names depending who you talk to.
The valve indicates a brake pressure issue in the system. If one half of the system has a drop in pressure an internal piston moves to one end of the valve from the centre position. This illuminates the dash light to indicate a brake system malfunction. Is your (brake warning) dash light illuminated? If so the internal piston is still moved instead of in the centre position. You can apply hard pedal applications to reset the valve, once your brake system is properly bled.
If you changed your MC you should bench bleed to remove air then bleed your brakes normally. Make certain to maintain brake fluid supply for bleeding so you don't draw air into the system. You can bleed numerous different ways but the power bleeders appear to be the most effective.
The valve indicates a brake pressure issue in the system. If one half of the system has a drop in pressure an internal piston moves to one end of the valve from the centre position. This illuminates the dash light to indicate a brake system malfunction. Is your (brake warning) dash light illuminated? If so the internal piston is still moved instead of in the centre position. You can apply hard pedal applications to reset the valve, once your brake system is properly bled.
If you changed your MC you should bench bleed to remove air then bleed your brakes normally. Make certain to maintain brake fluid supply for bleeding so you don't draw air into the system. You can bleed numerous different ways but the power bleeders appear to be the most effective.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
Proportioning valve, distribution valve, brake warning valve, whatever! The valve has numerous different names depending who you talk to.
The valve indicates a brake pressure issue in the system. If one half of the system has a drop in pressure an internal piston moves to one end of the valve from the centre position. This illuminates the dash light to indicate a brake system malfunction. Is your (brake warning) dash light illuminated? If so the internal piston is still moved instead of in the centre position. You can apply hard pedal applications to reset the valve, once your brake system is properly bled.
If you changed your MC you should bench bleed to remove air then bleed your brakes normally. Make certain to maintain brake fluid supply for bleeding so you don't draw air into the system. You can bleed numerous different ways but the power bleeders appear to be the most effective.
The valve indicates a brake pressure issue in the system. If one half of the system has a drop in pressure an internal piston moves to one end of the valve from the centre position. This illuminates the dash light to indicate a brake system malfunction. Is your (brake warning) dash light illuminated? If so the internal piston is still moved instead of in the centre position. You can apply hard pedal applications to reset the valve, once your brake system is properly bled.
If you changed your MC you should bench bleed to remove air then bleed your brakes normally. Make certain to maintain brake fluid supply for bleeding so you don't draw air into the system. You can bleed numerous different ways but the power bleeders appear to be the most effective.
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
you reset it after you get the system filled and bled. If you have an air path from the mc thru the bleeders on the rear you should be able to get juice to the rear brakes. It takes time, open 1 bleeder on the rear and fill the MC and walk away for a while. Let it gravity bleed, check on it in 15 minutes or so to see if the fluid level is going down. Keep it full. Or, go to sears or autozone and get a mighty vac and use it to suck juice down the line to the caliper
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Burning Brakes
Joined: Oct 2004
Posts: 920
Likes: 1
From: Shelby Township Michigan
you reset it after you get the system filled and bled. If you have an air path from the mc thru the bleeders on the rear you should be able to get juice to the rear brakes. It takes time, open 1 bleeder on the rear and fill the MC and walk away for a while. Let it gravity bleed, check on it in 15 minutes or so to see if the fluid level is going down. Keep it full. Or, go to sears or autozone and get a mighty vac and use it to suck juice down the line to the caliper
Just like he said. I would recommend that you slightly elevate the front of the car to help things move along. I found that the gravity bleeding worked great. Do the inner rear calipers first, then the outer.
Good luck,
Dino
8th Gear
Joined: Jul 2007
Posts: 8
Likes: 0
From: White River Jct., Vermont
like sixfooter says, it does take some time of front to back cracking of the bleeders. also, it's hard to get too, but if you have a mirror you can visually check the centering of the plunger by unscrewing the switch on the prop valve body and looking through the threaded hole. the skinny middle section lets the switch plunger lengthen (open) and shut off the light. when the valve shucks front or back its diameter is thicker at each end so it pushes the switch closed to ground and turns on the light. ever since i learned this the hard way on my jeep years ago, i also gravity bleed now just to avoid this hassle. i've had decent luck with the brake vacuums too. gravity and vacuum bleeding can also save the MC from damage- if it's an old MC there can be slight rust on the plunger rod because normally the pedal never pushes that far, so it gets surface rust. when the pedal gets pushed to the floor to bleed the brakes the surface rust scores the rubber seals in the MC and then the MC gets air trapped or fluid leaks by and you get a spongy pedal.
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
Thanks to everyone for the collaboration
I've found this awesome tech guide :
http://www.mbmbrakeboosters.com/inde...d=27&Itemid=86
So I think I have to (in order) :
- Testing Power brake booster
- Bench bleeding and testing MC
- Reset proportioning valve
- Bleeding the lines
To reset proportioning valve, I have to open front lines (that are clear) and close rear bleeder screw, so the pressure could build up and the valve commutate...
I've found this awesome tech guide :
http://www.mbmbrakeboosters.com/inde...d=27&Itemid=86
So I think I have to (in order) :
- Testing Power brake booster
- Bench bleeding and testing MC
- Reset proportioning valve
- Bleeding the lines
To reset proportioning valve, I have to open front lines (that are clear) and close rear bleeder screw, so the pressure could build up and the valve commutate...
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
Isn't there another mechanic's way to commutate my blocked proportioning valve???
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Yes -you have to pressurize the rear calipers.I have a tool that is the reverse of the Mighty Vac.It pumps up a tiny bit at a time.DONT PRESSUIZE WITH AN AIR HOSE-IT WILL COME OUT THE MASTER CYLINDER AND GO ALL OVER YOUR CAR.One way I used to do it in a pinch was to push 2 screwdrivers between the rear rotor and the brake pad,pushing the pistons in and pressurizing the system.Do it on all 4 pads in the rear at the same time that will be pushing 8 pistons in and yes thats 8 screwdrivers or wood shims if you have them.Make sure all rear bleeders are closed before you start and 1 bleeder in the front is open.
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
Yes -you have to pressurize the rear calipers.I have a tool that is the reverse of the Mighty Vac.It pumps up a tiny bit at a time.DONT PRESSUIZE WITH AN AIR HOSE-IT WILL COME OUT THE MASTER CYLINDER AND GO ALL OVER YOUR CAR.One way I used to do it in a pinch was to push 2 screwdrivers between the rear rotor and the brake pad,pushing the pistons in and pressurizing the system.Do it on all 4 pads in the rear at the same time that will be pushing 8 pistons in and yes thats 8 screwdrivers or wood shims if you have them.Make sure all rear bleeders are closed before you start and 1 bleeder in the front is open.
But I think I have to do a little work before...my proportioning valve is probabily blocked because I've just replaced the front to rear rigid brake line...now, with the valve blocked, there isn't enough oil in the rear lines and enough pressure too.
I think I have to add oil in the rear lines (like reverse bleeding with a large syringe from the right rear caliper bleeder)...
With the lines full of oil, I will try to pushing the pistons...
Can it work??
Drifting
Joined: Jun 2006
Posts: 1,912
Likes: 12
From: Schaumburg (Chicago) Illinois
This may be a dumb question but how long did you try to get oil back there? I just did a complete rebuild. None of the lines had oil in them as they were all new SS. Bleeding:
Fronts no problem. The rear took so long to get oil back there I thought something was wrong. but eventually if flowed. Brakes work great! In my younger days I manually bled the brakes wrong. I would let up on the pedal before I closed the bleeder.
1) minor pressure on pedal
2) open bleeder, pedal should go down but keep pressure on it. if it doesn't go down then fluid isn't moving.
3) close bleeder
4) release pressure on pedal. Pedal should come up.
5) repeat
If I am insulting your knowledge please excuse me. But there are alot of people who don't know how to do much with their cars. Alot of times the answer is going back to the basics.
Fronts no problem. The rear took so long to get oil back there I thought something was wrong. but eventually if flowed. Brakes work great! In my younger days I manually bled the brakes wrong. I would let up on the pedal before I closed the bleeder.
1) minor pressure on pedal
2) open bleeder, pedal should go down but keep pressure on it. if it doesn't go down then fluid isn't moving.
3) close bleeder
4) release pressure on pedal. Pedal should come up.
5) repeat
If I am insulting your knowledge please excuse me. But there are alot of people who don't know how to do much with their cars. Alot of times the answer is going back to the basics.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Hmmm I guess I should have read closer.You dont have a combination valve on your car.The block in the pic doesnt have the ability to stop flow its only a switch for the dash brake light.If your having trouble getting fluid to the rear you need to back up and start over.Put the master in a vice and do a good bench bleed.Put it back on the car hook up the lines and bleed the air at the master lines.Leave the master cover loose and off to one side a tiny bit so air can get in and not form a vacuum there by slowing the flow to the rear.Then open the bleeder on the LR inner caliper and wait for the fluid to show up.If you dont have a Mighty Vac you can create a little vacuum by using some of my previous post.On the LR inner with the bleeder still open pushin on the pistons by pushing in on the brake pad-close the bleeder and then release the pad-the pistons will try to come back out creating a little vacuum and helping to start the flow to the rear.Reopen the bleeder and wait for the fluid or repeat the above.
Melting Slicks
Joined: Jan 2003
Posts: 2,817
Likes: 21
From: Somerset, NJ
C-2 and C-3 Corvettes are a real pain in the *** to bleed at times. Do yourself a favor and come up with $60 and purchase a Motive Power Bleeder for your Corvette. I have owned Corvettes since buying my first C-2 back in early '71 a used '67 Vert and have been messing with these Corvette brakes for just as long. A couple of years ago I purchased a Motive Power Bleeder and it was the best thing I could of ever done owning two older Corvettes. I never had such a good pedal in both Vettes before making the purchase. With the Motive Bleeder you can bleed your Vette in as little as 20 minutes perfectly and never need help from anyone again as far as having to pump the brakes. Well worth the $60 I spent for mine. Here is a link to the Motive Bleeder you need Part #0105: http://www.trackhaus.com/brake-bleed...FRt2YAodsAG7dg
I don't think you are going to have to mess with your proportioning valve after using the Motive Bleeder. In all the years that I have owned my Vettes I never had to touch the valve. Any questions just ask.
I don't think you are going to have to mess with your proportioning valve after using the Motive Bleeder. In all the years that I have owned my Vettes I never had to touch the valve. Any questions just ask.
Last edited by ffas23; Jul 26, 2007 at 11:45 AM. Reason: Spelling
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
If you dont have a Mighty Vac you can create a little vacuum by using some of my previous post.On the LR inner with the bleeder still open pushin on the pistons by pushing in on the brake pad-close the bleeder and then release the pad-the pistons will try to come back out creating a little vacuum and helping to start the flow to the rear.Reopen the bleeder and wait for the fluid or repeat the above.
Thread Starter
Racer
Joined: Apr 2007
Posts: 251
Likes: 0
From: Milan
I bought a power bleeder (Motive) and speed bleeder valves
Now I've oil at rear calipers, but still no solid pedal an no pressure at rear calipers!!!
Should be the master cylinder!!
A friend of mine give me another used MC and after bench bleeding, I've tried to test it compressing the master cylinder plunger with a blunt metal rod...
With together mc ports closed (with inverted flare bolts) it's firm.
With together mc ports open, the front one squirt and the rear one trickle!
With only the front one closed the rear trickle again..
I think that's not really good? Another dead MC???
Could an incorrect booster pushrod adjustment cause MC failure???
Now I've oil at rear calipers, but still no solid pedal an no pressure at rear calipers!!!
Should be the master cylinder!!
A friend of mine give me another used MC and after bench bleeding, I've tried to test it compressing the master cylinder plunger with a blunt metal rod...
With together mc ports closed (with inverted flare bolts) it's firm.
With together mc ports open, the front one squirt and the rear one trickle!
With only the front one closed the rear trickle again..
I think that's not really good? Another dead MC???
Could an incorrect booster pushrod adjustment cause MC failure???
Last edited by Dream Bikes; Oct 10, 2007 at 04:45 PM.