I recently picked up an 2001 LW200 which has seena lot of salt, and the front calipers were sticking. I removed and cleaned everything up today, but now I can't figure out how to get the fluid restored in the lines. The standard bleed method, which is to pump up the system with the pedal andthen open and close the bleed valve at the caliper, is not working for me -I can't get any of the fluid to move down the lines. The fluid levelin the master cylinder has remained unchanged after many attempts.


What am I missing? Any help would be greatly appreciated.

You will need to manually open the proportioning valve and have it held open. With this open, you should be able to bleed it normally.





(there is a tool made for holding the PV open. It should be available thru a part store of you local GM dealer)

Thanks a lot for the advice - once I find it, and figure out how to hold it open, I'll submit a (hopefully) final report.

Update - I'm obviously in over my head.


Two lines leave the master cylinder and connect to a rather complicated 'block' from which the brakelines to each wheel emerge. Under that block is a complicated apparatus which I presume is the brains and brawn of the ABS. I see nothing accessible which looks like it might be a proportioning valve, or anything which I could manually hold open. I picked up a Haynes L-series manual today, and it says nothing about any special bleed procedure, it simply goes through the basic steps which are not working for me.


Unless someone can save my butt -since (1) it looks like I've got to spend money to make the system operational, and (2) I'm likely never to be capable of bleeding this system myself, and (3) as far as I can tell the brakes have never been changed (though there's more than50% pad left) -I'm going to replace all brake components incl. the master cylinder, then take it (carefully, emergency brake only) or tow it tothe qualified repair shop around the corner, and have them bleed the system and make sure the ABS works.


Good thing I kept both my day job - and my old car.

The PV would be the block you talking about (the one that has the lines out to the wheels). Look real hard at it and you should find a sopt that a too; should slip into and pull.

Hey thanks for your help, I'll keep trying before giving up altogether. I looked again tonight, closely, and I still see nothing, but I'll get my grubbies on this weekend and poke around a bit. It also occurred to me that it's entirely possible, since electronic components are involved, that I might have success if I turn the key on, or maybe even run the engine.

Just wanted to finally close this thread... after twisting off a bleeder on one of the rusted rear wheel cylinders in December, I took the winter off - then last week finally expanded the job beyond just the front calipers to replacing all active hydraulic components - including (and especially) the master cylinder. I'm pretty sure now that my whole problem was a failedMC (which was full of gunk)- 'cuz once I replaced everything, bleeding was a breeze. I just used one of those $5 one-man bleeders from NAPA. There was no need to mess withthe proportioning valve or anything else - I just connectedthe tube and bottleto each bleeder in the recommended sequence (RR, LF, LR, LF), pumped and emptied the little bottle until only clean fluid was coming out at each wheel - and ended the saga.