Brake system problems, proportioning valve?
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 1,012
Likes: 5
From: Granbury, TX
Brake system problems, proportioning valve?
The brakes on my ’82 have never been great, I have problems pushing through the staging lights holding ~ 2,000 rpm on a 3500 stall converter. I've replaced the front calipers, flex lines and master cylinder and pumped quarts of brake fluid through the system to bleed out the air. When I pump up the brakes as soon as I remove my foot, the brake light will illuminate. It will go off as soon as I touch the pedal again. This problem is beyond frustrating. 
Could it be the proportioning valve, or in the case of my '82 the combination, brake switch and proportioning, valve? If so where do you get one? GM has discontinued this item. Thanks much for the help.
Could it be the proportioning valve, or in the case of my '82 the combination, brake switch and proportioning, valve? If so where do you get one? GM has discontinued this item. Thanks much for the help.
Melting Slicks
Joined: May 2003
Posts: 2,076
Likes: 281
From: Dyersburg TN
I fought hard with my brakes until I tried a pressure bleeder. I did the pump and hold and vacuum but nothing worked well until the Motive unit. Vette brakes seem to take more to get right.
http://www.jegs.com/i/Motive+Product...00250/10002/-1
To reset the light, stomp the pedal hard. If it is working it will center the valve and the light go off. If you do have a failed valve, several places carry them:
http://www.ecklers.com/product.asp?p...4&dept_id=1050
http://www.ecklers.com/product.asp?p...9&dept_id=1050
http://www.jegs.com/i/Motive+Product...00250/10002/-1
To reset the light, stomp the pedal hard. If it is working it will center the valve and the light go off. If you do have a failed valve, several places carry them:
http://www.ecklers.com/product.asp?p...4&dept_id=1050
http://www.ecklers.com/product.asp?p...9&dept_id=1050
Melting Slicks
Joined: May 2003
Posts: 2,076
Likes: 281
From: Dyersburg TN
Motive
per posts I had already read, I did not try to use the chain hold down that came with the motive. I put a block of wood on top and a big C-Clamp. Also some recommend that you do not put brake fluid in the motive but just the MC. If you did not get a good seal, I can see how it might make a mess. If you do chose to put fluid in Motive, I would recommend pressurizing it with just air first. Watch the Gage to see if it drops. If not, open tank and add fluid.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 1,012
Likes: 5
From: Granbury, TX
per posts I had already read, I did not try to use the chain hold down that came with the motive. I put a block of wood on top and a big C-Clamp. Also some recommend that you do not put brake fluid in the motive but just the MC. If you did not get a good seal, I can see how it might make a mess. If you do chose to put fluid in Motive, I would recommend pressurizing it with just air first. Watch the Gage to see if it drops. If not, open tank and add fluid.
Le Mans Master
Joined: Apr 2001
Posts: 5,000
Likes: 1
From: Minneapolis, Mn USA
Clint
Dont use the Motive system as a fluid source. Only fill the MC with fluid and use the Motive bleeder as a pressure source. Pump it up to 15PSI and open the bleeder to bleed.
The motive bleeder is known to release brake fluid at pressure onto everything around it if you fill it up with brake fluid.
Here is my method which has worked great for me 3x already:
1) I fill the MC with Valvoline DOT3/DOT4 fluid (my preferred stuff)
2) Apply 15PSI from the Motive unit to the MC.
3) Crack open the bleeder until I'm satisfied. Don't let the MC go dry as you'll have to start over.
4) I then relase the Motive pressure by slowly loosening the Motive top cover or the MC seal C-clamp and refilling the MC before I move to the next bleeder.
When you do the rears, youll need to top-off the MC 2x for each caliper as they have the 2 bleeders on them, as you know.
Makes the whole deal childs play.
Brent.
Dont use the Motive system as a fluid source. Only fill the MC with fluid and use the Motive bleeder as a pressure source. Pump it up to 15PSI and open the bleeder to bleed.
The motive bleeder is known to release brake fluid at pressure onto everything around it if you fill it up with brake fluid.
Here is my method which has worked great for me 3x already:
1) I fill the MC with Valvoline DOT3/DOT4 fluid (my preferred stuff)
2) Apply 15PSI from the Motive unit to the MC.
3) Crack open the bleeder until I'm satisfied. Don't let the MC go dry as you'll have to start over.
4) I then relase the Motive pressure by slowly loosening the Motive top cover or the MC seal C-clamp and refilling the MC before I move to the next bleeder.
When you do the rears, youll need to top-off the MC 2x for each caliper as they have the 2 bleeders on them, as you know.
Makes the whole deal childs play.
Brent.
Last edited by MN-Brent; Sep 9, 2009 at 01:17 PM.
