no brakes

[d.h.]

I,ve been experiencing a lack or no rear braking on my dually for a few years now.Really a problem with my fifth wheel.I have taken to probably 15 different places and all (exept one) said they seemed fine.
The shop that did said ther was air in system. They purged it out with a tool at the antilock unit on the driver fender.They said either my master was at fault or the (rwal)was at fault.
I ordered master and installed that,but no improvment.I had front rotors turned and installed new pads July 30 before my holiday.Rotors are now blueish and warped from holiday.
This rwal unit is ordered in two pieces,elecrical side and mechanical side.Both are about $700 each. Is ther a way of checking or disabling system to check which one is at fault or should I take to the mechanic to diagnose


Thanks Dave

[DmaxMaverick]

If you pull the fuse or disconnect the module, it should be inert. They can be contaminated with air, but they will self-bleed over time (much less time than you're talking about). If you have no external leaks, it's probably the MC.

[d.h.]

I replaced mc

[HH]

Did you bench bleed the MC? How is the adjustment on the rear brakes?

[d.h.]

Did you bench bleed the MC? How is the adjustment on the rear brakes?

The master was bench bled properly and rear brakes are adjusted.This problem is from either mc or rwal unit.I,m leaning towards rwal as everything else has been replaced new.I know some mc's are bad right out of the box but i don't believe this to be the case.
I wish I could completly remove rwal unit pipe in new prop valve and be good to go.I,m thinking along these lines.

[DmaxMaverick]

Are you sure it is RWAL? I thought 98 was ABS. They are different.

[d.h.]

Are you sure it is RWAL? I thought 98 was ABS. They are different.

You may be correct. The unit is different than my old 90 chev I had.This one has more electronics to it.I was more curious if anyone has ever had a problem with this unit?I don,t think Canadian/American production have any differances regarding brakes?
With everything else being up to scratch I don't think there is anything left.

Thanks Dave

[DmaxMaverick]

The older RWAL did have air entrapment issues, but the ABS modules do not. They will self bleed very quickly. The greatest problem with ABS is they quit working, which leaves you with no ABS, but it is inert (as in not working, but no interference). Your problem sounds like a leak or bad MC. And, yes. Many bad MC's right out of the box. Are you losing fluid?

[d.h.]

Dmax There are no external leaks.I agree about mc possibly being bad but my gut is leaning towards that brake controller.Did abs braking not come out with new bodystyle? For what it's worth I'll replace mc again.

[DmaxMaverick]

I think ABS came along with OBD II, or there abouts (1996). Even early on, some models had RWAL, and some didn't. At first, it was a selected option, and later was standard. ABS was standard where it was available. The HD trucks (2500HD and 3500) usually lagged in the body style and tech features, so it's hard to tell. Your RPO sticker should indicate what you have or don't have. Your fuse block could also tell you something. If it has an "ABS" fuse, that's what it has. Also, if both MC lines go to the ABS module, then it's ABS. RWAL had only the rear brake lines going to the module.

If your rear brakes have a proportioning valve, it could be an issue. Otherwise, I'd still suspect the MC unless you find a leak or a damaged brake line. All this assuming your rear brake hardware is healthy and properly adjusted.