Try this master cylinder and brake bleeding method before you spend any more money.
Check the power brake booster by pumping up the brakes before starting the truck. While holding pedal, start truck. The pedal should slowly fall under your foot. If ti does not, the brake booster or the vaccum line to the intake is bad.
First, the master cylinder will be bleed by a process called, "Bench Bleeding". It is genrally done off the vehicle, but if you have two people it is much easier on the vehicle.
You will need two brake line ends that fit master sylinder that are long enough to loop back into the bottom of each reserviour. Attach each line and loop it back into its corresponding reserviour.
Fill with fluid and have someone watch the fluid for bubbles and to keep the fluid level from getting low. WARNING, fluid can shoot out of master cylinder and get into your eys so wear eye protection or watch out.
Pump the pdeal irraticaly with short abrupt pedal presses and see what the bubles look like that come out of the end of the lines that are looped into the master cylinder. If they are small and there are a lot of them, you have a while to go just on the master cylinder. Continue this while adding occasional half and full pedal strokes, continue until no more bubbles appear from lines. If it never stops, the master cylinder is bad.
If you get it to bleed out. Re-attach it to master cylinder. Go to Home Depot or hardware store where they sell clear poly-propelene, or any pliable clear hose, and buy about 4 feet of hose that will fit snugly over the end of the bleed nipple. Then get a liter or pint size container and a quart or 2 of brake fluid.
Place on end of the hose into the container.
Start by bleeding the brake farthest away from master cylinder and then the next closest and so on.
Run the hose from the container over some suspension part that will hold that point in hose higher than brake caliper or the turn in the brake hose if possible. Attach the end to the bleed nipple. Put some axle grease over the threads of the bleed nipple.
Pump the brake several times and hold. Loosen the bleed nipple until it releases fluid. Continue this process until the high point in the hose has been filled up.
Once you get brake fluid flowing you can continue to pump without stopping as the system is closed and no air can get in.
Finsish when fluid is clean bubble free and there is some change in the pedal feel.
Continue to pump the brake pedal while you tighten the bleed screw.
Repeat standard pump and hold then relase fluid procedure a few times for good measure.
Repeat this method in this order.
Start at Passenger rear, then go to drivers rear, then go to passenger front and then finish with drivers front.
If this does not give you a good pedal feel, you probably have a bad caliper or master cylinder. They can both leak and take time to notice as the pressure seal is a few centimetrs bleow the dust seal in both the caliper and the master cylinder.
If the vehicle sat for a while, water probably collected in the lowest parts of the sytem. However it takes time to migrate.
I mention this becasue I have seen steel lines blow out at low points with salvaged cars. Just keep an eye on them.
Saturday, October 29th, 2011 AT 5:59 AM