can anybody tell me what type of symptoms i mite get from a proportioning valve that isn't working rite?
i mounted a set of Dakota front discs on an A108 van. upgraded the rear drums to 11" units.
it all works great, but seem to get hot sometimes. and when that happens the front discs bind up. i can either stop where i am and let it cool down, or stop and bleed off the pressure. either way, i need top stop rite then and there.

the rear drums have no issues.

when it happens, everything is cool to touch, but the proportioning valve is hot.

can they do this?

In my experience, that problem is a turned cup or some gunk in your master cylinder that doesn't allow the fluid to come back when you release the brakes.

Not saying this is you problem 100%, but it was the last time I saw the symptoms you describe.

The hot prop. valve is a new one to me, however.

sb

Check the brake pedal free play. When I swapped to disc brakes on my '66 Dart the brake light switch held the pedal too far down and the relief port was covered. The pedal should move just a little before pushing the master cylinder piston.

_________________
Joshua

i have been weary of the master since i got it. it was not available "new" anymore. had to settle for a reman'd unit.
i don't have any freeplay in the pedal. i assumed that would have been the correct way to set it up, but it took lots of extra pumps to get any usable pedal pressure everytime i needed it. when i tighten up the play to a slight advanced push, it all worked except for this occasional tightening. and it doesn't do it all the time.
it happens most often during a lot of stop and go traffic. on long cruises, i mite find the pedal a bit low after a couple hours left alone.
i have driven it coast to coast this way.
ya mite say its been consistently inconsistent.
for a while i thought it was a heat issue because in the van, the MC is tucked up next to the exhaust side of the motor box. recently i have found the MC stays nice and cool.
when we get to the triple digit weather i do have to loosen the brake pedal rod a bit. sort like a winter setting and a summer setting.
the MC that was suggested for this app is from a B series van. it is for a non power assist, disc front, drum rear system.
maybe i got a funky MC?
or maybe the range of stroke on the B van is longer than the A?

if that was too much info. . .

could somebody please check the temp of their proportioning valve after about 30-40 min of stop and go driving?

If the relief port in the master cylinder becomes covered when the brake pedal is at rest then any fluid expansion from heating will cause pressure to build in the system applying the brakes. The master cylinder piston has to be free to return to it's resting position to open the relief port.

I really, really don't think it's a proportioning valve issue. Problems there would show up most likely as fluid not flowing through one part of the system or no proportioning resulting in premature rear brake lockup.

You do not have a suspended brake pedal so it's vital that you have an adequate return spring on the pedal linkage. The spring in the master cylinder is only to return the master cylinder piston to the top of the stroke.

_________________
Joshua

i have never thought to look for a return spring on the pedal.
i have never taken that out of the van. i believe it is as it always has been since the 10" drums all around.
i will check.

yes, there is a quite substantial return spring and the pedal returns to its full rest position with a BANG each and every time.

so its not a sagging pedal. . .

Good. Does the master cylinder piston also return to its resting position every time?

_________________
Joshua

as far as i know it does. but i can't see it at the end of the MC.
in the van it is mounted opposite from a car. its like it is mounted on the other side of the firewall. it is turned around.
i had to improvise a dust boot to keep road grime out of there, so i can't see it.
since i have the freeplay in the pedal tightened up to 0, i can tell i never have that sort of loose play. i think that tells me the piston is returning as it should.