No brake fluid to the rear wheel cylinders
You'll need to start bleeding the brake system at the Master cylinder to determine where the problem lies.
The lines coming out of the master cylinder will need to be loosened & bled there, initially you can just do the back ones to identify the problem, but once fixed, the system will have to be bled from the Master cylinder first, then the farthest wheel from it, then next farthest, then next, until you do the drivers wheel last.
This method of bleeding the brakes prevents air from crossing from one line to another, causing air to be left in the system.
Back to bleeding the rear brakes first: As someone pumps up the brake pressure, making sure the resivoir stays full, with the cap on between bleeding, and have the person pressing the pedal to do these thngs.
1. Always move the pedal slowly, pressing and releasing.
2. Never release the pressure on the pedal after bleeding a brake, until the line is tightened, then release slowly to prevent air from getting into the fluid.
You should of course get fluid at the master cylinder when you bleed it (or just replace it), then you'll need to bleed the line at the right rear wheel (first) a few times to get fluid if it's been leaking, then the left rear wheel. If you get pressure but no fluid to the rear and the master cyliinder did have pressure released when you bled it, there is either a restriction in the line itself, or the porportioning valve could be damaged. (unusual for the valve to go bad actually, inspect lines for damage such as being pinched if you're getting pressure but no fluid.
Final test if it hasn't been resolved-remove lines at porportioning valve & make sure fluid is leaving/entering there as it should. If you find it defective, a good replacement can come from a salvage yard, or you can buy them new.
Brake fluid on the floorboard under the dash near the brake pedal=bad Master Cylinder.
Feb 21, 2010 |
1996 GMC Jimmy