dcbltg

My 82 CE, 32K miles, brake warning light just came on last week and I'm lost for a solution. Master cylinder full, no visible leaks, light goes off when I tap the peddle hard, comes back on when braking. Braking is just OK. Any suggestions?

Peterbuilt

That light only comes on because there is a problem with the service brakes.
You might want to bleed the brakes to be sure that no air has entered the system.
Note the mileage after bleeding and if the problem returns then check for rotor 'run-out' or failing bearings.

dcbltg

Thanks for your help.

HeadsU.P.

Your Proportioning Valve has tripped. It sensed a low or unequal pressure in either the back or front system and triggered the light. As I found out last month, you may not get one drop of fluid on the ground but still have a leak somewhere. Sometimes air gets in past the caliper pistons. Sometimes the master is shot. Check all four rubber brake hoses and all eight connections for any sign of dampness.

Using the search box in the upper right corner, look at some past posts on this.
Enter: brake light on.

DUB

I would bleed the brakes and using a clear plastic tube attached to the bleeder fitting at the calipers I would watch for air bubbles.

Then write down the mileage and drive the car and see if it comes back on. If it does...see how many miles you went and for me that is an indicator on what I need to look for....especially if when I was bleeding your brakes I did see some air bubbles out of any of the calipers....unless I can visible see fluid leaking out of any of the calipers.

If this car is not driven a lot it can be a problem in the brake warning switch due to not being driven...and especially if the brake fluid looks like black coffee and there is some thick sludge at the bottom of the master cylinder.

If you do see air coming out of the bleeder fitting..make sure it is not fooling you due to you can get air to seep past the threads....and if you do have air in the calipers but no visible fluid leaks...your brake rotors can now be out of spec and need to be checked for proper indexing. Which possibly can cause for the wheel bearings to also be out of spec thus the entire rotating assembly out of whack...and that will need to be addressed so it can be put back into spec as it should be and how it was designed.

DUB

Ryan Menzies

OP,

The RED light should change intensity/brightness between service brake (Prop valve) or electrical (Park brake). It tells you what circuit is causing issues.

Ryan Menzies

Can anyone confirm my above post? This was the quick standard way of separating this issue quickly. This was in newer Domestic vehicles but I'm sure that test is what lead me to my park brake switch on my 72 this winter.
Getting old .... the car and me.

Cheers

Peterbuilt

Hi Ryan,
On a C3 the intensity of the bulb is the same no matter if the parking brake or the service brakes cause it to light up.

DUB

if all is correct.

The only time it may change is if the ground circuit or terminal is dirty/corroded and not getting a good complete ground path.

DUB