Hey guys, I have been researching this for about 2 hours now and still can't find my answer... so here we go... I have a GM proportioning valve for Disc/Drum setup with a metering valve that leaks when I bleed the brakes. I understand if there is a line leaking from one of the two outlets it pushes the piston of the metering valve on the proportioning valve off center and then starts leaking out of the nipple on the front. Now with that said. This thing continuously leaks from this nipple, not by much, but enough for me to get about a drop from it at least every hour or so. I have tried resetting it and also note that I do not have any leaks at this time from any of the lines (nothing is wet anywhere. When I go to bleed the brakes they are not stiffening up the way they should be, they are still spongy (but am getting a steady flow of fluid from the lines with no air present), but a great deal better than what they were before I bled them. Is this normal with this kind of proportioning valve??.. keep in mind I also have vacuum assist.. This is the first time I have installed this kind of proportioning valve (the one that is installed right now) on an older vehicle so it is new territory for me. Now, I bought this new proportioning valve that purposely does not have this metering valve to let you know that the brakes are leaking and it is for the disc/drum set up. Can anyone think of anything I can do to try to fix my issue with the other valve before swapping this out or should I just go ahead and do it.. the old proportioning valve seems like a nuisance anyway. But what are your thoughts??... is there something special to bleeding the rear brakes with the original proportioning valve that I have installed? Here are some pics:
the metering valve ,if you have one ,only "delays" brake pressure to the front dics until the rear drum springs have a chance to unseat. so when you bleed the brakes you will get fluid to the front disc. what you're resetting is the plunger that should be "balanced" between front and rear brake systems. "unbalanced" condition means pressure is built up in one system and not the other, causing the plunger to offset and you have provisions for a "brake" failure light. if you had to "reset" the valve that means fluid is moving in one system but not the other(fluid leak or air being compressed). bleed from longest to shortest line with engine off. I've had cars that I thought were bled and still had air. Keep bleeding. no leaks then you shouldn't have to add fluid, air or not.
I just installed a new one of these for a friend. THis time it came with a plug and it said to remove the white nylon plug and install this knurled plug only while bleeding, this saves you from messing with the metering valve. It worked, I never used one before but now I have it I will in the future
You wouldn't believe what the shop manual tells you to do to pedal bleed a truck with one of those damn valves in it. I just limped it down to Monro Muffler and paid them $20 to pressure bleed it every time because it was such a pain in the ass. IIRC, you were supposed to do it with the engine running, and slowly depress the pedal. You had to be really slow, or you would trip the valve and had to reset it. To reset it, you were to open a line at the master and pump it once, which makes a mess. And that's the factory manual directions for 1989 R/V/G/P, which is squarebody trucks, vans, and panel vans. With my current van I was able to gravity bleed it because the master is up higher and got a pedal that way. But it should not leak from anywhere, either, which tells me something must be wrong with yours.
okay, Well it sounds to me rusty that I should probably swap this out to the new one I just bought because of the leak, do you agree? It should not be leaking period and I do not have a brake warning light setup on my truck so I should be okay correct? What do you think fordor? Anyone else? I will try to bleed it more, but it is only leaking from the front metering valve reset.. I do not think it is supposed to do that, is it?
well I installed the new proportioning valve and can get everything to not leak except for one thing... The main line going into the front of the splitter from the master cylinder. I have loosened/cleaned/etc. multiple times and am to the point where it is barely leaking... I will screw with it tomorrow My question: how stiff are the brakes with the engine off for a power boost set up supposed to be for one of these new aftermarket master cylinders? I understand it may bleed slowly to the floor but this thing is pretty much hovering 1/2 an inch from the floor and wont bottom out (which is good), but it is extremely easy to push to the floor up until that point. I take it that some of the pressure is bleeding off from this leaking connection, but the rear brakes shouldnt be giving me that much of a problem. I take it that I must still have air in the lines, but I will try to tighten that one connection up and then bleed everything again.
are all the brakes new? are the rear brake shoes adjusted? what else was changed? brakes out of adjustment, not "worn in",wrong pedal ratio or bad/worn hardware will give you a low pedal.
Replace the main line and recheck for any leaks. There should be NO leaks or seepage anywhere. With the porportioning valve (why are you using one?) you have to SLOWLY press and release the pedal while bleeding or it will trip. Yes, you have to then release the pressure by opening the line at the valve or push-in the release pin (if equipped). usually you only install a porportioning valve if you NEED one to even out the braking action. IS your car the same weight as the car that the porportioning valve came off? Same front and rear brakes?
Valve should never leak anywhere. The GM combo valve seems to confuse lots of people when bleeding. When the valve gets off center the system will never bleed correctly. Some instructions say to push the pin in to center the valve, or attach a special clip to hold it there. Never had any luck with that method. Either the pin would not push in, or it was too hard to get to to even try. To center the valve the thing to do is this: Close the bleeder on the part of the system that is not getting good flow. Attach a test light to the warning light terminal on the valve. The terminal is the ground for the light. If the light is on, then the valve is not centered. Crack open a bleeder on the 1/2 of the sysem that was getting good flow while trying to bleed. Now have an assistand slowly push down on the brake pedal until the light goes out-stop pushing on the pedal and close the bleeder. The piston in the valve should now be centered and you should be able to bleed the system as usual by starting at the furthest brake from the master.
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