Brakes / MC / Switches / Bleed Question

Doug E · 07-27-2014, 01:59 PM

Thought I'd check in with the brain trust to see what I missed in my diagnosis.

Car is an '81 SC ... here are the details:

Problem started out to be no brake lights. Checked the fuse and bulbs and both were good so I replaced the 2 switches on the master cylinder. Brake lights worked but the pedal went soft and and MC started leaking. It appeared to be the original MC but not sure (I know I haven't replaced it in my 14 years of ownership).

Replaced the MC and put in the 2 switches that I had just replaced on the old MC. Put fluid in the MC on the bench. Drained the old fluid from the system and bled the brakes using a Motive bleeder.

The pedal is firm and there are no leaks but now the brake lights aren't working. Switches are properly connected, fuse and bulbs still OK.

My initial thinking is maybe there is an air bubble in the MC which is preventing the switches from working properly so I was going to re-bled the system the old school way by having someone pump the pedal.

Any other thoughts ?

TIA, appreciate it.

Doug E · 07-29-2014, 03:00 AM

Haven't had time yet to re-bleed so just bumping for any other ideas ... thanks.

Caledonian · Caledonian's Garage

Obvious question, but if you short the wires to the switches do your brake lights work?

crsjulaw · 08-06-2014, 12:45 PM

How do short the wires on brake switch to test the brake lights?

$ Short · $ Short's Garage

On my 88 which is vacuum assisted I had to start the car. After running a few seconds the brake lights were working. I found this after doing a search here on this forum.

Doug E · 08-09-2014, 10:52 AM

Finally got back to this project and the problem was that one of the new brake light switches was bad ... and on top of that it was leaking around one of the seals.

After replacing that new switch with another new switch (and then I did the 2nd switch just to be safe), re-bleeding and buttoning it all back up I now have brake lights again !