This one has me confused. I was bleeding my brakes today on the 70 and noticed that every once in a while the pressure switch on top of my distribution block would leak from the top terminal/plug area (pic below). I have this unplugged because the wiring harness is out of the car (along with the engine, trans, etc). It will not leak here every time, but once in a while it will do it. I swapped the plastic pressure switch with a spare, but it did the same thing. What confuses me is how it leaks out the top where the terminals/plug goes, not at the base where it bolts on the distribution block. The system (not master) was basically dry when I started bleeding, so maybe that has something to do with it. The pressure switch never leaked before with the original brakes hooked up and operating well (6 months ago). Any ideas? Thanks! Further background: 70 Grabber, new discs in the front, new cylinders/hardware in the back. All the rubber hoses are brand new (front and back). The only used parts are the master cylinder (4 wheel drum)/hard lines/distribution block.
I haven't messed around with the distribution block. Have you tried testing the brakes without the switch in. It seems that there could be a leak under the switch. If you have an extra distribution block try that and see what happens.
Corbin If it leaks under pressure it will suck air ( therefore air in system ) you will need (A) change out the switch or (B) plug it.
Yeah, that makes sense. It's weird that it leaks up and out the top of the plug. I also changed the switch with another spare I had (not new, but worked when taken off the car) and it leaked again. It doesn't do it all the time, which is confusing as well. The part is probably cheap enough at Napa to just replace it anyway and hope it fixes the problem. Edit: Just look at Napa, Kragen, Rock Auto, and can't seem to find the switch.
I got mine (disc/drum) used off E-Bay for $29.99, could not find it anywhere else. I took it apart and cleaned it, and got a good look at it. The area where the switch plugs in is essentially a "dead chamber" sealed off from fluid by o-rings on each side. The piston inside is centered when both brake systems are good. When one system or the other is bad, the piston is forced to the front or rear which allows the pin inside the switch to drop into a machined groove in the piston and activates the brake light on the dash. If it were me, I'd disassemble it, clean it, and see about replacing the o-rings... Russ
Does anyone have an actual part# for the Switch? I bought one a few years back at advance auto parts for $5. I cracked mine, while getting a little /ahem/ enthusiastic tightening it (the nylon sure got brittle ...) but now everywhere I go (autozone, advance, o'reilly, napa) looks at me like they have never heard of this 'thing' you call a 'brake pressure switch' or at least a confirmed interchange? Stangs? Broncos? thanks -AP
Corbin; try one of these: Wilwood Engineering, Pn#260-11179. It is a distribution block, proportioning valve and brake switch all in one. The switch is a brake light switch, not a pressure switch. I have one I am going to use on my stuff, but don't need the switch. Let me know what you think.
