dirtybird81

after looking over the hydraulic side of everything brake,i found the switch for the brake light located on the combination valve/proportioning valve(mounted to the anti-lock brake unit)leaking. does anyone know if this switch can be repaired or replaced individually. i priced a new unit, which is discontinued,for like 300 bucks.ebay had it listed for like 500 any ideas?

Injuneer

How did you determine that it is not on because of a differential in the pressure being applied to the front and rear braking circuits? "Looking over the hydraulics" doesn't sound adequate. For example, how would you detect a master cylinder that is leaking internally between the front and rear pistons?

Did you verify that the switch on the proportioning block is actually in the "on" position? Did you verify that the "BRAKE" light is not on because of a problem with the E-brake switch?

I have seen the differential pressure switch stick in the "on" position, and I have seen reports that it can sometimes be cured by making an extremely hard stop, which should only be done in a totally open area, like an unoccupied parking lot. But before taking that chance, I would suggest a more thorough analysis of the problem. You would assume all liability for the results of such action.

dirtybird81

I recently had a master fail and have a replacement before replacing them (bought a new booster as well) i inspected the rest of the brake system for leaks and wear,as well as caliper functionality and mechanical soundness ,and found no problems.i did find a leak from the switch on the combination valve tho and before replacing the other items i thought it would be wise to stop the leak at the switch. the light came on after i verified the leak at the switch body. i am like you and assuming that the failed master caused a pressure issue. wanted to seal the leak and prevent damage to the new master before replacing it. do you know if the switch is removable? Thanks for the help.

Injuneer

Unclear, but appears you have already replaced the master - would have been useful info up front. Did you follow the correct bleed procedure outlined in the factory manual, starting with the bleeders on the ABS motor pack?

The switch is a block with 3 threaded ports visible. What part is leaking? If its any of those ports, may just need to be tightened. If it's the switch, that is replaceable.

It also has two bolts that go through the opposite side of the motor pack, and pull the switch block against two small pipes with o-rings, that connect the switch block to the motor pack, and allow the fluid from the block to flow into the motor pack. The bolts that hold the switch block on the side of the motor pack are not visible unless you take the plastic cover off the outboard side of the motor pack.

I have never taken it apart, just going by the factory manual.

dirtybird81

My apologies for the omission of info. I have not replaced the master or the booster yet, I have only procured the parts. It pleases me that the switch comes separately, as there is brake fluid coming from the inside of the female end of the switch(this is the only evidence of external fluid leakage i have identified). You wouldn't happen to have the part number or availability of the switch, would you? If there is anything else information wise that i can provide to better help the situation, let me know. Again, thanks for the time.

dirtybird81

the black connector portion is where its leaking from.

dirtybird81

Found the replacement for the connector portion mentioned above 88983914,is the gm part number and it retails for around 15 bucks. versus buying a 300 dollar part, id say its a good deal.i just want to reiterate that the reason im replacing this is because it is leaking thru the sender body,the black portion shown in the picture above.