Combination valve problems

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Mopower73

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Okay so switched over to a disk brake from a factory drum in the front if my 73 duster. Took all the parts I needed off of another car but the combination valve was missing so I bought the one from inline tube for front disk and rear drum brakes. Well I bled the system and what not but my light will not go off! And the brakes are funny because if you hit them hard and fast it comes to a stop mid way and only locks the front brakes then if you ease off the pressure a little bit the pedal will then go down farther and lock the rear and fronts together like its supposed to. It is bugging the heck out of me and I donno what to do. Open to all options thanks!! Btw everything is brand new master cylinder, calipers, lines, and so on....
 
That is a strange situation. You know, most of the prop valves that mopar made were all the same. A 4dr was the same as a 2 dr, And even a pickup truck was the same. So, if it were me, I would find one from a pickup truck from the 80's or early 90's. Actually, they really do not do that much. They are more like a delay valve than a proportioning valve. even if you ran without one, I'll bet you wouldn't know much different un less you were doing some very extreme braking and even then you could just go to some smaller diameter wheel cylinders in the rear to make the bias correct. I think maybe the wildwood adjustable prop valve would have been a better choice though. They just delay the rear brakes from locking up before the fronts lockup. this prevents a spin out. Good article for adapting abs to older cars in the mopar action mag of the last few months. This would be the real way to prevent skidding. All the parts are in the J-yard. One thing though, you have to make sure that all the parts are working together correctly and that the system is totally bleed right and that the drum brakes are adjusted right. Everything has to be right and double check everything. You must use the correct master cylinder and the rod and pedal must be right. Double check all the basics first. This is all I can tell you for know without more information. (I might get some flack from some of this advice on the prop valve though).
 
You have a defective combination valve...see if you can return it.

I got 2 different ones from Inline Tube and both were defective right out of the box.

If you do some research you will find complaints about that. I believe the defective rate was like 25%-33%.

They are not machined properly and you can't get the light to go off.

Get an original one...there is a company that sells parts to rebuild them...see the link below...

https://www.musclecarresearch.com/mopar-parts

I ended up using parts off the 2nd one I got and put them on my used/original valve just to make it look pretty.

I wouldn't buy anything from them, I bought some lines for my duster and a couple of them were way off with the bends. The only reason I used them was that they are local to me so i could drive over there.

Paul


Okay so switched over to a disk brake from a factory drum in the front if my 73 duster. Took all the parts I needed off of another car but the combination valve was missing so I bought the one from inline tube for front disk and rear drum brakes. Well I bled the system and what not but my light will not go off! And the brakes are funny because if you hit them hard and fast it comes to a stop mid way and only locks the front brakes then if you ease off the pressure a little bit the pedal will then go down farther and lock the rear and fronts together like its supposed to. It is bugging the heck out of me and I donno what to do. Open to all options thanks!! Btw everything is brand new master cylinder, calipers, lines, and so on....
 
Wow that's crazy thanks a lot for that info I'll have to think about getting that rebuild get and possibly finding one at a junkyard. Well I'll never be buying anything from them again
 
... Well I bled the system and what not but my light will not go off!....

does "what not" mean that you centered the pressure imbalance switch like you are supposed to? If not, the light will not go off. I have never done it, but there are threads that describe it. Basically, you crack one or both nuts, while a helper slightly pushes the pedal to keep air out, and the springs should center the switch, or maybe a bit more involved, so read up.

As I understand, when an adjustable proportioning valve is set properly, the fronts will lock up slightly before the rears (test in a wet parking lot). I assume the factory valve should work the same, but don't know.
 
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