Brake Light won't go off!

**hskerprid** · 05-07-2009, 12:16 PM

Just replaced my Master Cylinder, front pads ( rear's are fine ) Bled the brake's with a mechanic friend of mine. I still had to pump the brakes to get them to firm up and then the light would go out. Now it's on constantly and I have a spongy brake pedal..........Any suggestions guy's???

**chengny** · 05-07-2009, 07:19 PM

I'm new to this forum as well. But, I frequent several other forims of this type - and one thing I have leaned is that you must include some detail about your truck. At a minimum tell us the make model and year. Trust me, people will be much more willing to help if they know up front what you are working on.

As far as your brakes are concerned - they still have air in the lines. If your mechanic friend has bled them and left you with spongy brakes and a constant warning light... well, he is either not much of a mechanic or not much of a friend.

Anyway, if your are now all on your own, try this trick:

Park your truck on the steepest inclinel that you can find (nose up) and with the engine off slowly and deeply pump the brakes. Keep a full pint of clean brake fluid handy and constantly monitor the master cylinder chambers. If one chamber seems to be dopping add fluid as necessary. Turn the truck around and do the same thing with the rear end on the higher level.

This may or may not work the air bubbles out. If it doesn't, you will have to properly bleed the system again.

One positive note: quite often the brake lines on these GMC trucks will allow the air to migrate up into the master and it will purge itself with time (without reopening the bleeder fittings).

**hskerprid** · 05-08-2009, 08:27 AM

OOPS! I usually tell people that info, brain-fart I guess. It's a 1995 Silverado ext. cab Z71 HD. I will try the incline technique and see if that help's. THANKS!!!

**Blazerado** · 05-08-2009, 08:35 PM

If you have 4-wheel abs this will not apply but if not you need to bleed the RABS valve. Its a royal pain to do, but it has a sensor in the top of it that if there is a lack of fluid will ground itself to the valve housing.