Brake Warning Light

[LG57]

1993 Explorer Sport. I'm getting a brake warning light intermittently.(not to be confused with ABS Light) There are no leaks. The master cylinder is less than a year old. Occasionally, after backing out of the driveway, then moving forward, on first application the front brakes will grab, skidding the tires. At this time the warning light comes on and the ABS motor growls. I confirmed the growl is from the ABS motor by hitting it with 12 volts off the battery. It is noisy. Any ideas? Could the new master clyinder be leaking internally? How to test it?

 

[Roadrunner777]

There are only three things that, by the wiring diagrams, will light the brake warning light:
1) Turning the key to START (bulb test of sorts)
2) Using the parking brake
3) Low fluid signal from master brake reservoir

I have seen in other vehicles where a sensor checks that the shuttle in the master cylinder is out of range, but that's not the case here, there is apparently no such sensor.

Anyway, put this together with the uneven braking... I have to ask in my kindest possible voice: Have you checked the brake fluid level? It would explain everything.

 

[LG57]

Hmmm. It didn't look low, but I'll give it another look. Could be the level sensor is hanging a bit. Thanks for the thoughts.

 

[kmack]

I had this light coming on recently also. It was low fluid level in the master cylinder. But it was caused by very thin brake linings as my brake pads needed to be replaced.

 

[LG57]

I had this light coming on recently also. It was low fluid level in the master cylinder. But it was caused by very thin brake linings as my brake pads needed to be replaced.

Thanks for the reply. As suggested by Roadrunner, I checked the fluid level. It didn't look excessively low, but I added fluid anyway and gave the level sensor float a jiggle to make sure it wasn't stuck. Havn't driven it yet, but will report back.

 

[LG57]

Update. Problem is cured. The brake fluid was not "low", but I added a small amount anyway and gave the float a jiggle. Seems ok now. Thanks for the suggestions. Just goes to show, check the obvious stuff!