To do this correctly you will need a pressure bleeder, but if you don't have one you can do it manually be sure the brake fluid is full in the master cylinder before starting and have another person pump up the brakes from inside the truck and once they are pumped up hold there foot on the pedal while you or another person opens the bleeder valve on a wheel (only do one wheel at a time). The pedal will go to the floor when you open the valve so be sure the person inside does not take his foot off of the pedal until you close the valve or you will suck air back into the system. When you open the valve or bleed the air from the line do so until you only get fluid out of the bleeder, no air bubbles at all. You will need to bleed each wheel more than once. Be sure to keep the master cylinder full of fluid at all times. Hope this helps.
Let's start by getting to know a bit more about your background. Have you ever bled brakes before? Assuming you have, then you know the importance of making sure all bleeder screws will open before starting the bleed process. And assuming you don't have an issue with the ABS system that you are trying to bleed, you just bleed the brakes like a normal vehicle. Start with the wheel furthest away from the master cylinder and move closer. So this usually means Passenger Rear, Driver's Rear, Passenger Front, Driver's Front. I prefer to use a length of clear tubing that fits the bleeder screw, then install a check valve, followed by another length of clear tubing in to a clear jar. The check valve is very effective at keeping air from entering the lines so that you can do 1-person bleeding without getting a sore hand from using a vacuum pump.
SOURCE: 2000 gmc both rear tire oil leakage.
You are correct, it's not brake fluid. Check the level in your rear axle, it sounds like you have bad seals in the axles allowing the rear differential gear oil to leak inside the brake drums.
This is a heavy weight oil, 80 or 90 weight. This leakage will ruin your brake pads, and if enough leaks out, your rear differential will blow. The seals aren't expensive, but it's a lot of labor to pull everything apart to get at the seals, plus new rear brakes. My Ford ( and I'm sure your GMC) require removal of the rear axles to change the seals. Good Luck! countrycurt0
SOURCE: Bleeding Brakes on a 2001 Silverado Z71
Tony,
When bleeding brakes after the system has been opened for service (you didn't say if you were doing any work on the master cylinder) you should start with the farthest wheel away from the master cylinder, which is the righ rear. Fill the master cylinder, then have an assitant "pump up" the brake pedal. Tell them to hold it down firmly, then open the bleeder on the wheel cylinder(s). Do not release the brake pedal until you have closed the bleeder valve again. You'll know when the air is out - there won't be any more bubbles. Since this vehicle is 2001, this would be a great opportunity to flush the system. Just make sure you have enough brake fluid (DOT 3 or 4, depending on your vehicle). Good luck!
SOURCE: brake bleeding procedure on 2000 vw golf
get a one man bleeder kit from halfords (about £7) and then you can go around the car and bleed the brakes without a assistant, you just attach the tool to the nipple on the caliper, loosen the nut, press the brake pedel a few times till there is no more bubbles in the hose and then move on to the next corner, there is a specific way to go around the car but if you start at the back and finish at the front it should be ok
SOURCE: Brake pedal still goes to floor 2000 GMC Jimmy
It's very possible to be the master cylinder, the o-rings on the piston could be worn, letting the fluid seep back through instead of getting full pressure through the lines. Could also be the brake booster.
Try changing the master cylinder first, which is cheaper and easier, and see if there is a difference, you'll need to bleed the brakes again.
To check the booster,
With the engine off, pump the brakes until the pedal is hard, then hold pressure on the brake pedal and listen for air escaping, or the pedal goes slowly to the floor, Do that after the master cylinder has been changed, at least that will be eliminated.
Testimonial: "Hadn't thought about the O-rings on the rod thanks for the idea. Great Idea Thanks!"
SOURCE: bleeding brakes 2000 suburban wsith ab
Why were the brake lines replaced?
Sounds like the mastercylinder may have run dry. You have to bench bleed the master and then DO NOT allow fluid to run low, while bleeding brakes...
if master cylinder runs low on fluid and air gets in, almost impossible to bleed with out releasing the lines and bleed master it self.
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