Also, that thing in the middle of the first picture that is cylindrical seems like it ought to have a pin in the middle of it that would then protrude into the fitting. Is it possible that the pin was blown out of it?

 

Is there a valve in the area of the proportioning valve that you can remove (after the bolt and spring were removed) and take a photo of? I'm wondering if there is a bad O-ring on it that might need to to be replaced? Also, can you take a photo of the top of the bolt that you removed from the proportioning valve? The photo I see shows the inside of the bolt.

 

There is no valve that is removable after the spring or if there is I don't know how to remove it.

I ended up taking out the proportioning valve which was not easy with its corroded fittings. I cleaned the top and bottom fittings with brake cleaner. Then I cleaned what I could of the whole thing. After putting everything back together I tested the vacuum with a brake bleeding pump. At first the bottom fitting leaked at 10 inHg vacuum. When I tested the top fitting I could hear air immediately upon applying vacuum. It was leaking around the base of the fitting where it meets the unit. This was not the fitting that was showing the leaking originally. Anyway I fashioned a seal for it out of a vinyl glove. Now that fitting stays leak free at 15inHg. Now I tested the bottom fitting and it too stays leak free at 15inHg. I did not make a gasket for the bottom fitting.

Is 15inHg a sufficient test of the unit's ability to stay leak free? The bleeder instructions say not to apply more than 20inHg vacuum when bleeding brakes because it will damage the system. When the unit was in the truck before it was freely leaking from the bottom fitting. Will it go back to leaking when I put it back? Thanks.

 

Keep in mind, that your brake system can operate at pressures north of 1000PSI.......

 

Yes, I thought so. Wonder why the bleeding vacuum kit says that over 20inHg can damage the system. Is "inHg vac" comparable to psi? It seems that this port is acting as a pressure relief valve of some sort. That word be congruent with the person above's (in the forum's sequence not any higher power, lol) experience of having the problem with the unit and its replacement. Just mulling. After putting everything carefully back together the unit still leaked in the same spot and manner. Perhaps not quite as much fluid is being lost. If that port is a type of pressure relief (the outside of the fitting has a standard bleeder connection as does the top fitting) then is it possible that the release of some fluid is necessary to perform the proportioning function? Also the sensor that goes onto the unit is obviously the ABS sensor but does anyone know what it senses (e.g. pressure, presence of fluid, turbidity, etc)? Thanks. - j

 

The proportioning valve really doesn't have anything to do with ABS, that will be a separate unit. Proportioning valve just regulates pressure to front and rear, so you get 'balanced' braking. (about 70% front, 30% rear.) The 'sensor' in there is just a switch. If one braking circuit fails, (blown line, or whathaveyou) the valve in there moves, and closes off the low pressure side, so you still have some brakes. The little switch there then turns on the "Brake" lite in the dash.

At this point, I would just replace the prop valve. You REALLY want your brakes working properly.

 

I have the same problem. Leaks from the bottom with the rubber cover. Brakes seem good and no dash brake light on. I wrapped it with a towel for now. I did buy a new one on ebay and will be replacing it soon. Are those two rubber covers just that? A cover?

 

Yep! That is all they are

 

I agree but I don't want to change the proportioning valve only to find out that it makes no difference. If that sensor only trips the brake light then I have other problems too. My ABS light is also on and comes on at the same time as the brake light. Do both of the lights get triggered from the lack of appropriate pressure in the system, for instance? I just don't want to go on an expensive wild goose chase. The kid I bought it from said he changed all of the brake hardware, pads, rotors, calipers, etc and changed the master cylinder and bled the brakes. It seems that he was doing that wild goose chase. Any more thoughts?

 

If the prop valve is leaking, you need a new one.

If the prop valve is triggering the brake lite, then yeah, it will annoy the ABS as well.

In all reality, I think the ONLY time the brake lite will be on, without the ABS light also being on, is when you are parked with the E-brake set.