Not a comforting sight to see either while driving 40+ down the road, I thought the brakes felt funny lately. I tried bleeding them awhile back it seemed to help for a little while then today it began doing it again.

Coming home with my handicapped brother in the van the brake light came on which obviously made me nervous, the van would still stop so I wasn't panicking, I pulled into a Gas Station to check things out, Master Cylinder was full, lines all looked good, no leaks anywhere I was like what the heck thinkin maybe there was short with the light.

I realized later with these old Fords there is a Proportioning Valve where the light plugs in at so I'm thinking maybe the valve is on the fritz, the light stays on now if I turn the key, I thought about blocking off one circuit on the Master cylinder with one of my plastic fittings and trying to force the valve to reset if all possible if that is indeed the problem. I do not want to spend money needlessly but at the same time I don't want to risk my brothers safety here if there is potential problem with the braking system.

Would appreciate any help on this, thanks.

 

It would help to know what the van is and if it has ABS.

 

Sorry bout that, the Van is an 85 E-150 Club Wagon XLT, it does not have ABS.

 

*[Update]*


Jacked it up and did some tests, with both front and back raised I placed my toolbox (which is not at all light) on the brake pedal making sure I still some residual vacuum in the booster to maximize pedal pressure. The front brakes hold strong can't budge the wheels but the back brakes are another story can still turn them albeit with some resistance I know it should be like the front and not able to move them at all.

Will try bleeding the back brakes and see if that does anything to improve it. As I said in the first post I bled them last time this happened and even tried flushing the system with brand new fluid before bleeding, it seemed to help for a little while then this, so i'm starting to wonder if air isn't entering the system someplace overtime can't see how. The fluid btw is Prestone DOT 3 Synthetic which i've used before on this van and our other car with "0" Problems so I don't think it's the fluid at least I hope not .

Could the Master Cylinder going bad cause this? Cause if it's the Proportioning Valve i'm probably screwed because I can't find them new anywhere around here, I would end up going to Pick N Pull and I don't like getting brake parts out at the Junk Yard.

 

Well bleeding it fixed it temporarily, today it did it again this time the pedal went to the floor, but after pumping the brake pedal for a few seconds, the pedal firmed up again and the light went off.

Drove it around a bit and the light would come on intermittently, pumping the brake would usually turn the light off. Now i'm puzzled, can't still be air in the line I made sure there were no air bubbles..

 

Well I replaced the Master Cylinder but i'm beginning to think that was a waste of time and money because it still does it just not as bad as before. Maybe the old MS was going but it wasn't dead yet.

Anyway I do notice fluid on the sides of the MS and the lines under it though I don't think they are leaking. This only happens after actually driving the Van not just sitting it in and pumping the brakes.

So I'm wondering if the MS could be overflowing and why?

The parts guy at Kragen mentioned it could be a Wheel Cylinder or a line, the lines all run clear and don't appear to be clogged, the wheel cylinders aren't that old either they were just replaced a year or two ago, guess when I get some more time I could pull it apart and inspect them don't really want to if I don't have to though.