1990 Dak, 2wd, front disc, rear drum. The Front accumulator/proportioning valve was Nassssstttyyy. Trucks been sitting at least 7 years, and I figured the inside was as nasty as the outside of this unit. I removed the accumulator spring and see a red tube in there. Removed the other end and all I see in there is some kind of plastic retainer or filter...it had some sand/grime built up on it so I cleaned it with brake cleaner, but I don't see how to remove it or if I need to. There's another rod/valve/spring assembly behind it that runs the length of the unit, and I can push on the rod and it seems to move freely. I've got the unit soaking in mineral spirits (removed the two gaskets), but is there any way to remove that other rod assembly? If not I guess after soaking going to blow all the ports out with air and call it a day?

 

So the plastic retainer comes out, but it gets me no further. I see a rubber diaphragm and gasket around the rod but see no way to get anything out further. The rod is a push/pull and using air I see it connects the two end ports or blocks them off from each other. The rod doesn't spring on its on, it is push one way and pull the other. Is this the normal behavior or is it supposed to spring back? I'm concerned it's gunked up inside not allowing a spring return.

 

Well I see now, it's a shuttle piston....I was wondering why there were two connections to the M/C and I see now it's to detect a pressure differential. So, a high pressure side due to a leak somewhere will cause the piston to block off the leaking side, and in turn grounds out the idiot light switch. Here's a good video on explaining this, as it seems to be particular to Mopar. I was getting confused because most of the other videos show a single M/C connect and TWO connections to each of the front brakes. But Mopar has the two M/C connections and ONE connection to a splitter for the front brakes in order to detect this pressure differential. So, it would appear mine is working correctly.