On my 79 malibu I just put a new rear with disc brakes factory gm metric calipers front and back has manual brakes and factory manual 7/8 bore master cyl while changing rear I lost all of the fluid out of my master cyl going to rear brakes I got everything back together and started bleeding brakes after several hours of bleeding I still cannot get a brake pedal the issue seems to totally be rear brakes you can pump brakes up loosen bleeder on front brakes and shoot fluid across building but when you try to bleed rears very little pressure if you ever get any pedal at all it's less that 1/4 way up from floor and if the rear bleeders are opened you lose it all after first time .... I pushed little button on the end of factory prop valve no help I've bled the master I've put containers at both rear wheels with fluid in them with plastic hose going from bleeder into fluid worked pedal back and forth and get a lil air doing that I left it set for 2 hours gravity bleeding refilling master every 30 mins so it didn't go dry and still pedal is only 1-2 inches off floor and very spongy .... I did put a adjustible prop valve to rear but removed it trying to get this thing figured out .... Any thoughts ?
Brake issues need help......
- Thread starter willtow
- Start date
Willtow,
1. Do you have a disc/disc proportioning valve. The stock disc/drum unit has a 10lb residual valve that is needed for drum brakes. The disc/disc unit does not have this. I don't think this is your issue though.
2. Are you running a stock 7/8" bore gbody manual brake master cylinder? If so, the reservoir for the rear brakes is may be too small to supply enough fluid to the rear brakes. You can add a 1979 buick riviera, with 4 wheel disc brakes, reservoir to the gbody master or go with another master cylinder with the proper volume.reservoir.
3. Since you lost all your fluid to the rear brakes, you need to remove your master cylinder from the car and bench bleed the master cylinder again. Because of the angle of the firewall and the way the master cylinder is mounted pointed up at an angle, there may be air in the master cylinder. I think this is your main issue.
4. The last thing, though a remote issue, is that you have low drag, metric calipers on the rear.
1. Do you have a disc/disc proportioning valve. The stock disc/drum unit has a 10lb residual valve that is needed for drum brakes. The disc/disc unit does not have this. I don't think this is your issue though.
2. Are you running a stock 7/8" bore gbody manual brake master cylinder? If so, the reservoir for the rear brakes is may be too small to supply enough fluid to the rear brakes. You can add a 1979 buick riviera, with 4 wheel disc brakes, reservoir to the gbody master or go with another master cylinder with the proper volume.reservoir.
3. Since you lost all your fluid to the rear brakes, you need to remove your master cylinder from the car and bench bleed the master cylinder again. Because of the angle of the firewall and the way the master cylinder is mounted pointed up at an angle, there may be air in the master cylinder. I think this is your main issue.
4. The last thing, though a remote issue, is that you have low drag, metric calipers on the rear.
You tripped the safety in the combo valve. If you have a disc/drum master cylinder you'll never build enough pressure to reset it. You need a disc/disc combo valve & a disc/disc master cylinder.
Tommy
Tommy
