Recently swapped the rear end which of course meant removing the brake lines and backing plates etc. After installing 12 bolt, bled system and now only when pushing hard on the pedal, the brake light comes on, ... then goes off when releasing pedal, brakes work fine. Re-bled again, still does it, - brakes work fine. (normal braking, light doesn't come on)
Anyone know the cause?
-- Edited by 1965CS on Wednesday 22nd of August 2012 10:05:33 AM
Incredibly, lost only a few drops of fluid and kept the hose high to prevent air entry -fluid loss when doing the swap. The light is by a pressure switch on the proportion valve and used an assistant to bleed the old fashioned way. Pedal movement seems the same as before, and brakes seem fine too. Only when pushing hard it lights.
-- Edited by 1965CS on Wednesday 22nd of August 2012 10:49:04 AM
Too much movement maybe? I've seen a sensor/switch that triggers right on the brake pedal itself .. if the pedal goes down too far it'll light. Could be you left too much slack in the adjustment when you reinstalled them. Bleeding the rears can be a pain when you've got the axle dangling (if you're holding up the body instead of stands under the axle) you can leave a high point that can be a real beach to get the air out of.
How did you bleed them? Friend on the pedal, suction or reverse pressure?
(forgive me if you already know this....but) Always assume there is air trapped in the system front to back once you crack open a brake line/associated hydraulic parts, so when you bleed you should have to add fluid several times to the res. Its a good idea to cycle new fluid through when you can as it doesn't get done very often, breaks down over time, ruins your seals, and since your already there and brake fluid is cheap.........;) Is yours a dual system (separated res for front and back)? I had a similar issue, my front brakes were good, but back brakes were bleeding down under hard braking due to a bad wheel cylinder. No leaks that I could see, bled the system three times, nothing changed, then I changed the back cylinders and bled, never had the issue again. A pain. I know. But good luck!!
Thanks for the info, I may double check the rear cylinders even tho there is no apparent braking issues, could be like you had. It is a fairly new dual system w fr disc and I did add fluid while bleeding.
(normal braking, light doesn't come on)