Brake fliud leaking through warning light switch?

[Platonic Solid]

Why is Brake fliud leaking through the brake warning light switch on the combination valve (proportioning valve/ distribution block). Do I need a new combination valve or do I just replace the switch? Or is there some other possible cause?

Thanks,
Svend

 

[TOM B]

Yep this happens all the time. I think napa auto still sells the switch or go to a mustang place. O yea, you need the switch only and most of the time you dont have to bleed the brakes, just do it fast.

 

[Platonic Solid]

Cool, Thanks! Napa didn't have it, but Mustangs Unlimited does.

 

[Platonic Solid]

The vehicle I’m working on is my girlfriend’s son’s 1985 LTD Wagon. I went to the used bookstore yesterday and pickup up a Haynes manual (gotta love it – only $4).

The cutaway picture of the pressure differential valve shows “O” rings on the center shaft before and after the brake warning light switch. Doesn’t this mean that brake fluid should not be entering the area of the brake warning light switch?

If I’m correct, can this valve be rebuilt or should a new one be purchased from a Ford dealer (since none of the part stores seem to carry it)? And Dang these things are expensive! The closest I can find online is this one from Mustangsunlimited priced at $180!!! Is there a cheaper way?

I’ve also learned that the pressure differential valve on this car incorporates a metering valve with a bleeder rod. The front brake bleeding instructions state: “push in and hold the bleeder rod while bleeding the front brakes”. Does this mean it becomes a 3 man operation: One to press the brake pedal, a second to operate the caliper bleeder valve, and a third to press the bleeder rod?

I even took the brake warning light switch off my 72 Coupe and tried it on the 85 LTD (the switches are identical), but fluid still leaked through it. It’s worth noting that no fluid was visible in the brake warning light switch hole of the 72 Mustang’s differential valve.
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