Bleeding ABS controller

[wrenchinup]

I put a new master brake cylinder in my 97 diesel ram. The ABS controller isnt letting much fluid through, making bleeding hard so I took it out and will probably put a pipe in it’s place. So if anybody knows if any problem that might result from that I’d appreciate the advice. I got fluid to gravity bleed the fronts fine, got the master and the combination unit bled fine. ABS controller gets fluid to it but after many attempts at typical bleed procedures it won’t drip any fluid on its outlet port and just lets a small amount throo on a pedal push, and I’m wondering if that’s normal or a sign of an obstruction or if it’s toast. A previous owner removed the ABS wires from the rear wheels and it only had rear ABS to start with. Thanks

 

[wrenchinup]

Well I think the valve, which I was calling the controller might be OK, as I was able to suction fluid through it fine from the master cylinder and combiner by putting a pipe on the outlet of it. Then to test the line to the rears I put a schrader valve on one end of a clear hose and put the other end of the hose in the line to the rears, which connects to outlet if RWAL ( rear wheel anti lock) valve under the combiner, and put a bicycle pump in the Schroeder valve with one rear wheel pipe disconnected from the T on the differential. Well it was just way too hard to push air throo it, in fact it barely took any air at all, so I’m pulling the tank out which i need to do anyway to put a new fuel sending unit in. So I’m keeping the valve in there as nobody carries new ones anymore, not the dealer or anybody. A lot of guys are disabling their ABSs by unplugging the HCU under the dash. But my early 97 (March) just has rear wheel ABS which is a whole lot less complicated than the 4 wheel system. Also, the 4 wheel drives are a lot easier to unplug because the speedo doesn’t share the abs sensor, it’s getting signal off the transfer case.

 

[wrenchinup]

Forgot to say, I’m pulling the gas tank so I can replace the brake line from the rear end to the ABS valve. I don’t have any question, just posting all this in case anyone runs into bleeding problems with the valve. Mine only needed bleeding because I replaced the master cylinder, which put some air into the valve, but replacing the calipers and wheel cylinders emptied the valve. I’m still not sure if I’m going to need the scan tool I have seen mentioned as supposedly required for bleeding the valve. My rear wheel only ABS only has two solenoids inside it and my Service Manual says nothing about a scan tool

 

[CVX20]

RWAL never did much for anyone when it was working.That's why you don't see it anymore.If it were my truck I would go and buy a proportioning valve and install it in place of what you have.You'll never notice the difference driving it.The only thing might be that if you have a State Inspection it probably won't pass.JMHO.

 

[wrenchinup]

Thanks, the wires to rear end are long gone and that valve makes bleeding a pain. I’ll look for a proportioning valve

 

[Moparfanatic21]

Thanks, the wires to rear end are long gone and that valve makes bleeding a pain. I’ll look for a proportioning valve

Eliminating the RWAL won't affect your speedo. You might be able to actuate one if the solenoids to bleed the valve. There also is a company the rebuilds them. I would bet your problem is in the proportioning valve that is on the truck.

 

[wrenchinup]

Thanks, the brakes were working when I replaced all the cylinders and both calipers, so doubt there is a problem with the proportioning valve. And since my last post, I've been able to suction fluid through both the proportioning valve (which my service manual calls a "combination valve") and the RWAL valve (which some also call a pump because it has the solenoids) just below it. All the fittings are standard "inverted flare" fittings so I just stuck a fitting and short pipe into the outlet of the RWAL pump and pulled fluid through both, from the master. I still haven't had time to replace the rear main line behind the tank but am hoping I can bleed it all when I'm done. I'm guessing my only question now is, just how fast does fluid pass throo the pump and the proportioning valve normally? It sure doesn't leak out, but it does suction out. I'll bypass the pump with pipe if I need to, since there isn't any RWAL wiring left anyway but I'd like to leave it in just for in case I decide to sell the truck some time. I may just have to wait until I finish it all up to find out if it works. My suction tool did seem to pull enough fluid through, up to the rear line. The fronts don't go through that pump, being only rear Wheel Antilock

 

[wrenchinup]

BTW, that pump, or valve, that only the rear line passes through, from the proportioning valve, is also called a hydraulic control unit (HCU) in my service manual. (Its not available anymore from the dealer but there are some new and used ones on Ebay) Its got the two solenoids in it which is supposedly why its best to use a scan tool to bleed it, but I did see one video showing how to do the cycling of the solenoids while bleeding by hoisting all four wheels and putting it in gear, running putting it in drive and hitting the brakes which engages the ABS. But a scan tool does the cycling also.