We've done everything we can think of on my son's 94 3500 to get rear brakes and they still don't work. We've put new shoes on the rear, the new larger size GM wheel cylinders, a brand new NAPA master cylinder, bled the brakes till the drive way was soggy, and everything else short of replacing the wholesale brake system components. Right now with the rear axle jacked up off the ground, you can put it in gear with the engine running and stomp the brake pedal clear to the floor and all it does is drop the rpm's a little and the wheels turn freely. This thing is really really getting on my nerves. He's got that old 81 Dodge sitting right next to this one with no power brakes or none of this anti lock garbage and it will stop on a dime. There is a lot to be said for simplicity.
Any ideas where to look before I do the fire test on this junk? I just hate to start wholesale replacing that RWAL brake garbage because I'm sure they are dealer items and will probably cost more than the truck is worth.

 

Something still isn't right, I guarantee that's not the way they were designed to work. I use the jack the rear up and stomp on the brakes method to remove rear drums all the time. They stop instantly ABS or not and will pull the engine way down.
Any other symptoms, mushy/hard pedal etc?
Are the new shoes installed correctly? There are a front and rear shoes, not sure on a Ram but on other vehicles it's possible to install them backwards, then they don't work worth a darn.

 

I doubt it has anything to do with the RWAL system. I would think that a quick way to check that is to pull the fuse for the ABS and see if it effects the stopping. What about the proportioning valve?

 

Ditto on the proportioning valve. From what I've read, it's the only thing left. Try removing the linkage and manually putting it in it's max open postion. If that helps some, replace the bugger.

 

My hay days are from the pre rwal system too and I have my opinions too. I can't express myself completely so I won't start. When you bled the rear cyls, how much fluid did you get at a time? Was it forceful or just a dribble? When the truck is jacked up in the back do you have the safety stands under the axle tubes or is the axle hanging? If you have low fluid flow while bleeding, try cracking the line at the flex hose and try it again, if flow increases, the flex hose is bad. try cracking the line going into the load proportioning valve and see if you get the flow. if you do the problem is in the valve, if not go to the main proportioning valve under the hood (I think that is where it is located on a 94) and crack the line going in to the valve. Then the rwal valve the same way. You should notice a big change in flow when you get on the upstream side of the problem.
Good luck. Let us know what you find.

 

When they put my used axle in from the accident, it had absolutely zero for rear brakes. I mean it literally had no stopping power coming from the back. I could stomp the brake while I was on glare ice and the back would keep spinning while the front was locked! I put the GM cylinders in and adjusted them. It took quite a few clicks (I took both my shoes off and that still wasn't enough ) to get them to grab, then the next week I adjusted them up again and now they are just about perfect. The front still locks up before the rear on ice, but not by too much.

 

Short shoe to the front if I remember correctly.

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Pedal is still squishy like stepping on a plum and goes to the floor after it stops. Its like something is leaking by. According to the service manual, the front brakes are not supposed to develop pressure until the rear shoes are in full contact with the drums. Then the valve lets the pressure go through to the front brakes. What I couldn't believe is that with the rear end sitting on blocks, I couldn't even stall the engine at idle stomping the pedal clear to the floor. The shoes are adjusted until they are almost in constant contact with the drum but not quite. We adjusted and centered the shoes and adjusted again and again. I can't believe I got a bad master cylinder from NAPA but I guess it is possible but the brake stopping power didn't change at all even with the new one installed.
Pulled the rear sensor wire from the rear end to see if they would work any better, no change at all. Unplugged the controls up front, nothing.

 

Mushy sounds like there is still air in the system. Did you bench bleed the master cylinder before installing it?
On most masters bleeding a new one after it's installed is almost impossible, you have to do it on the bench. The air stays trapped in the high end of master and will never come out with regular bleeding because air rises to the top. If you didn't bench bleed you may have pumped air into the ABS unit which requires a special bleeding procedure.
Sometimes you can get lucky if you have a steep bank near by backing and going forward up it. The tilt can allow trapped air to rise out into the reservoir.

If this doesn't help you may have gotten a faulty master, it happens.

 

Do you have a factory manual outlining the bleeding proceedure for the ABS system? I know that on other cars that I have worked on with ABS, the sysem could not be bled in a conventional manner. It required the pressure to be relieved from the brake system while bleeding the fronts with the key off. Rears where done by just cracking the pedal and openning the rear bleed valve, the ABS pump would run and force the fluid through the system.
You may want to get a hold of a manual, these ABS systems are a bit qurky and bleeding it by the book is the only way your going to get a satisfactory result.

Good Luck

 

Try bleeding the brakes with the wheels on the ground and a lot of weight in the back of the truck. The load porportioner (RWAL) adjusts the breaking power of the rear wheels. If there is no weight in the back there is not much breaking power.

If you have (AIR BAGS) And you carry alot of weight, the porportioner will be fooled by the lift . Even with alot of weight you will have very little rear brakes.

MP

 

Yep, read the manual every page that had anything to do with brakes. Can't remember if we bench bled with the hoses now or not. May have to do that again.

 

I agree on the bench bleeding. My dad's one friend put a new master cylinder on his truck, bled at the wheels, and it wouldn't work at all. So I took it off and bench bled it. Then reinstalled and bled all of the calipers and wheel cylinders. Good as new then. Had it happen on a 1974 Buick too, ending up doing the same thing. Good luck.

 

What is bench bleeding and how do you do it?

 

There are usually some little plastic hoses that come with the master cylinder or you may have to buy them. The little hoses are hooked up to the ports on the master cylinder on the bench and run in to the reservoirs on the master cylinder below the fluid level obviously. The piston is then pushed in repeatedly, after the reservoir is filled with fluid obviuosly, until all bubbles are removed from the cylinder. I have installed them on the vehicle and bled them there too with great success. Takes less time to hook up the brake lines and therefore less time for air to get back into the cylinder again too. Bottom line is that bench bleeding is nothing more than priming the cylinder before installation or connecting the lines up.

 

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