Red "brake" light on dash after caliper replacement
 

Hello everyone,

Thanks for your help, in advance...

I have a 1986 300E that had a left rear caliper frozen. I replaced the caliper and both rear brake hoses. At the same time I replaced both the rotors and the pads. When I went to go bleed the brakes, I have a red brake light on the dash illuminated and little to no pressure (really almost zero) to the rear brakes and plenty of pressure to the front.

My service info says, if the red light is on, I must reset the button on the front of the master cylinder. I see no switch. If I tap on the resevior the light on the dash flickers. If I depress either of the black test buttons on top of the resevior, the light stays on. If I unplug the floats, the light goes out.
I seem to have air in the master cylinder bore marked H, as when I bleed it there with a partner, foam comes out. The other part of the m/c bore has pressure.

I went to the ABS unit and it has some pressure going in from the m/c and almost zero going out of the H port back to the rear wheels.

I have used a vacuum bleeder (do not have access to a pressure bleeder) and a partner. SO far, zero success. Is there such thing as a reset pressure button (like on the old Volvo's) that could be inhibiting fluid flow, since I opened up the system?

Thanks again for the help!

William

Can you post a pic of the reservoir? Never heard of a test button and want to know what you have going on.

The reservior is partitioned off internally and the rear (H = Heck = Rear) has almost no volume. You need to completely fill the reservior and keep it full during the bleeding process.

Got some PMs about the internal wall inside the res and low fluid seemed to be the issue, I also noticed that Benz had an updated resevior with only one switch/float and no test button (and therefore no ability to push to test the light)...

There was fluid in it, but not enough...

Thanks!