The Rodding Roundtable
Motorhead Message Central => Rodder's Roundtable => Topic started by: Rob on April 17, 2007, 04:44:10 PM
I have little hair left from pulling it out, I'm stumped
Since replacing my front brake set-up this winter, I have had no rear brakes....
My set up is as follows
1" bore corvette style master cylinder-7" power booster, all under the floor.
From the master cylinder to the rear, I have a 10 lb residual valve (wildwood) to OEM proportioning (combination) valve from an '87 S10 and then on to my rear (drums, '85 pontiac Bonneville)
For some reason, since I've been trying to bleed the rears, I've lost pressure to the rear brakes, the fluid has just started to "dribble out" where as before is squirted out across the room. This has started since I changed from the adjustable prop. valve in the rear to the OEM style. What I have noticed is that the rear chamber of the master cylinder has air bubbles coming out of the hole in the floor when I press the pedal with the M/S cover off. I also remember reading here some time ago that the Wildwood residual valves were problem prone. Could either of these situations be the problem. I'm really getting tired of spending $$ and not getting the problem fixed!
For what it's worth, the front set-up is from ECI, 78-81 Camaro calipers with rear rotors, with a 2 lb residual valve. I wasn't getting huge front brakes when I first tried this set-up out, but the folks @ ECI suggested it might be the adjustable prop valve I was using, which is why I replaced it in the rear.
I'm REALLY stumped and frustrated, and would be forever grateful if someone has an answer.
Thanks
I have previously had trouble with some GM proportioning valves that will sometimes shuttle when bleeding and won't return. By shuttle I mean that the piston inside moves when you bleed, say, the rear brakes and treats it like a leak and shuts off further fluid flow. The worst was on a '79 Riviera that I owned for 197,000 miles. Every time I did a brake job it happened and I had to take the brake warning switch out and move the piston back to center with a pick. It took me a long time to figure that out.
Just a thought.
Charlie
That is a possibility, since the reduced fluid occured during the last bleeding marathon. I forgot to mention that one of my ongoing issues is that I can't seem to get the rear brakes bled, I'm getting constant air bubbles. That's why I was wondering if it's my M/S or residual valve that is the culprit, although I was told not to worry about the bubbles coming out of the hole in the floor of the M/S
QuoteI was told not to worry about the bubbles coming out of the hole in the floor of the M/S
This is the compensation port, and if there is air coming out of it, the master cylinder is not bled.
This is the compensation port, and if there is air coming out of it, the master cylinder is not bled.[/quote]
I assume then i would have to re-bench-blled the M/S. Would this account for (a) constant air in the line during bleeding, (b) no brake pedal feel and (c) no rear brakes?
Thanks
Quote from: "Rob"This is the compensation port, and if there is air coming out of it, the master cylinder is not bled.
I assume then i would have to re-bench-bleed the M/S. Would this account for (a) constant air in the line during bleeding, (b) no brake pedal feel and (c) no rear brakes?
Thanks[/quote]
Yes..Yes & yes...The master can be bled on the car...follow the same procedure you use for a bench bleed...Get ALL the air out of the master & then work your way back.....
I agree that the prop valve is closing off the rears it needs to be reset to the center ... i think you can push it over at the rubber cap on the valve.
Im sorry but im dumb. Ive never used a prop valve.. I didnt use residual valves till a couple years ago and dont know why i use em now. Even with under the floor m/c units..
Dave
Quote from: "Rob"I have little hair left from pulling it out, I'm stumped
Since replacing my front brake set-up this winter, I have had no rear brakes....
My set up is as follows
1" bore corvette style master cylinder-7" power booster, all under the floor.
From the master cylinder to the rear, I have a 10 lb residual valve (wildwood) to OEM proportioning (combination) valve from an '87 S10 and then on to my rear (drums, '85 pontiac Bonneville)
For some reason, since I've been trying to bleed the rears, I've lost pressure to the rear brakes, the fluid has just started to "dribble out" where as before is squirted out across the room. This has started since I changed from the adjustable prop. valve in the rear to the OEM style. What I have noticed is that the rear chamber of the master cylinder has air bubbles coming out of the hole in the floor when I press the pedal with the M/S cover off. I also remember reading here some time ago that the Wildwood residual valves were problem prone. Could either of these situations be the problem. I'm really getting tired of spending $$ and not getting the problem fixed!
For what it's worth, the front set-up is from ECI, 78-81 Camaro calipers with rear rotors, with a 2 lb residual valve. I wasn't getting huge front brakes when I first tried this set-up out, but the folks @ ECI suggested it might be the adjustable prop valve I was using, which is why I replaced it in the rear.
I'm REALLY stumped and frustrated, and would be forever grateful if someone has an answer.
Thanks
If you por. valve is a brass GM style with the place to hook a wire on top to a light, take a ohm meter and touch one end to the pin on top and other wire to ground and see if you get a reading. if so the valve has shuttled ond you will have to open the front bleeders aud pump the pedal to let it center. Check with meter again to see it you have no reading and it is centered again. If I remember right this is the way to do it.
Quote from: "Kctom1"Quote from: "Rob"I have little hair left from pulling it out, I'm stumped
Since replacing my front brake set-up this winter, I have had no rear brakes....
My set up is as follows
1" bore corvette style master cylinder-7" power booster, all under the floor.
From the master cylinder to the rear, I have a 10 lb residual valve (wildwood) to OEM proportioning (combination) valve from an '87 S10 and then on to my rear (drums, '85 pontiac Bonneville)
For some reason, since I've been trying to bleed the rears, I've lost pressure to the rear brakes, the fluid has just started to "dribble out" where as before is squirted out across the room. This has started since I changed from the adjustable prop. valve in the rear to the OEM style. What I have noticed is that the rear chamber of the master cylinder has air bubbles coming out of the hole in the floor when I press the pedal with the M/S cover off. I also remember reading here some time ago that the Wildwood residual valves were problem prone. Could either of these situations be the problem. I'm really getting tired of spending $$ and not getting the problem fixed!
For what it's worth, the front set-up is from ECI, 78-81 Camaro calipers with rear rotors, with a 2 lb residual valve. I wasn't getting huge front brakes when I first tried this set-up out, but the folks @ ECI suggested it might be the adjustable prop valve I was using, which is why I replaced it in the rear.
I'm REALLY stumped and frustrated, and would be forever grateful if someone has an answer.
Thanks
If you por. valve is a brass GM style with the place to hook a wire on top to a light, take a ohm meter and touch one end to the pin on top and other wire to ground and see if you get a reading. if so the valve has shuttled ond you will have to open the front bleeders aud pump the pedal to let it center. Check with meter again to see it you have no reading and it is centered again. If I remember right this is the way to do it.
there what he said, that was how we did them... :idea:
This happened to the sons s10. To recenter we opended a front bleeder and spiked the pedal hard 1 time, doing that repositioned the spool in the master.. The light on the dash went out ! Then did a normal bleed job.