Rear brakes locking up

[The_Hammer]

I have a 96’ Ram 2500 4x4 with 4-wheel ABS. The ABS system hasn’t worked in quite some time which is fine by me as the last time it kicked in I almost went through a stop sign and into an another truck.

 

The problem I’m having is the rear brakes will lock up with relatively light pressure. So far I have:

 

• Inspected the rear brakes and checked the adjustment, nothing was wrong.

• Replaced the front calipers, pads, and brake lines.

• Installed a new master cylinder

• Thoroughly bleed the entire system.

 

I’ve had this happen before on a different truck (non-ABS) and the culprit was a malfuncting combination valve. The problem is I have yet to find a replacement for my truck. I’m also wondering if the ABS unit could have an internal leak which would cause this issue? Any ideas?

[dave110]

I never knew they had 4WAL in 96. Other than that what you have done is what I would have suggested.

[The_Hammer]

14 minutes ago, dave110 said:

I never knew they had 4WAL in 96. Other than that what you have done is what I would have suggested.

 

Apparently it was an option.

[dripley]

Does it have one of those levers between the bed and the diff that adjust pressure based on load? I have read about them but have no experience with them.

 

I think my 96 had 4 wheel anti lock, but that was a long time ago.

[The_Hammer]

24 minutes ago, dripley said:

Does it have one of those levers between the bed and the diff that adjust pressure based on load? I have read about them but have no experience with them.

 

I think my 96 had 4 wheel anti lock, but that was a long time ago.

 

No lever. 

[dave110]

I was going to suggest the load valve too after I thought about it. Are you sure it's not there? Maybe the lever/rod linkage has fallen off and the valve is stuck in the loaded position. I know only certain years had them, not sure which ones though.

[The_Hammer]

4 minutes ago, dave110 said:

I was going to suggest the load valve too after I thought about it. Are you sure it's not there? Maybe the lever/rod linkage has fallen off and the valve is stuck in the loaded position. I know only certain years had them, not sure which ones though.

 

Me no gottie lever.

 

[Bullet]

Same here, load valve.  Only other thing I could think of is corrosion on the rear caliper pins which would not allow the rears to fully disengage.  Which would heat them up tremendously and lock fairly quickly when applied. 

[dripley]

I dare day he does not have rear calipers either. 

[The_Hammer]

47 minutes ago, Bullet said:

Same here, load valve.  Only other thing I could think of is corrosion on the rear caliper pins which would not allow the rears to fully disengage.  Which would heat them up tremendously and lock fairly quickly when applied. 

 

Front disk, rear drums.

[Bullet]

4 minutes ago, dripley said:

I dare day he does not have rear calipers either. 

Oh yeah...96 model.  I was thinking since mine has them.  And of course it could be argued that I wasn't thinking at all. 

[The_Hammer]

@Bullet No worries man 

 

 

At this point I believe it’s an internal issue with the ABS and will bypass it for the time being. I literally do not have time for this truck’s crap right now. It failed an inspection for a cracked windshield which is being replaced in the morning. Right after leaving the inspection place the brakes up and took a dump. I really believe this truck hates me.

Edited June 5, 2019 by The_Hammer

[The_Hammer]

I just bled the entire system again to no avail. Also the pedal still sinks to the floor with a brand new (not a reman) master cylinder. I couldn’t bypass the ABS unit due to no one in town having the proper fittings. Was hoping to isolate the issue but whatever. Hopefully it’s good enough to pass inspection until I can figure this garbage out.

[BBHD]

9 hours ago, The_Hammer said:

 

At this point I believe it’s an internal issue with the ABS and will bypass it for the time being. 

 I think it is too. I recently went through a similar situation on a 99' Durango where the pedal would bleed down. On the ABS unit you should have a couple plastic vent caps, pop them off with a screwdriver. You can use a straightened paper clip stick it in where the plastic cap came off one at a time and have someone press the brakes. If the paper clip moves the ABS is bypassing which lets the pedal bleed down. I had an extra ABS module from another Durango I swapped it with and it is good now. 

[The_Hammer]

@BBHD I’ll check the valves this evening. If it’s the cause of my issue I’ll order this and be done. 

 

https://www.summitracing.com/parts/sum-g3906/

[Mopar1973Man]

Neat valve... That would be awesome to set the ratio to front and rear braking. 

[The_Hammer]

5 hours ago, Mopar1973Man said:

Neat valve... That would be awesome to set the ratio to front and rear braking. 

 

I had one on my 82’ K5 Blazer and it worked great.