2004 Dodge RAM 3500 Brake Proportioning

[brianharrison]

Here is the other part out of the service manual for the operation of the EVBP.

DESCRIPTION - ELECTRONIC VARIABLE BRAKE PROPORTIONING
Vehicles equipped with ABS use electronic variable brake proportioning (EVBP) to balance front-to-rear braking. The EVBP is used in place of a rear proportioning valve. The EVBP system uses the ABS system to control the slip of the rear wheels in partial braking range. The braking force of the rear wheels is controlled electronically by using the inlet and outlet valves located in the integrated control unit (ICU).

OPERATION - ELECTRONIC VARIABLE BRAKE PROPORTIONING
EVBP is able to decrease, hold and increase rear brake pressure without activating full ABS control. Upon entry into EVBP the inlet valve for the rear brake circuit is switched on so that the fluid supply from the master cylinder is shut off. In order to decrease the rear brake pressure, the outlet valve for the rear brake circuit is pulsed. This allows fluid to enter the low pressure accumulator (LPA) in the hydraulic control unit (HCU) resulting in a drop in fluid pressure to the rear brakes. In order to ease the rear brake pressure, the outlet valve is switched off and the inlet valve is pulsed. This increases the pressure to the rear brakes.

The EVBP will remain functional during many ABS fault modes. If both the red BRAKE and amber ABS warning indicators illuminated, the EVBP may not be functioning.

Brian

 

[Wrenched]

Hi Bill
I have a 2004 Dodge 3500 dually with a Cummins Diesel engine. Around 85,000 miles, I had to replace the rear brake calipers - they were seizing and not working, or dragging.

It sounds like this could be your problem - the front brakes would do all the work and go in short order.
After that fix I could easily feel all 4 wheels braking when I pressed hard on the stop pedal.

When I replaced pads and rotors, I upgraded to a pad that was blended for towing. The rotors are slotted and drilled - it all helps.

The trailer brakes need to be adjusted regularly or they will be weak. On my previous trailer, a 2010, 40' Raptor - 16,000 lbs. I was surprised to find when checking that they needed a lot of adjustment to get them to the point where I could really feel the trailer pulling on hard stops.

I wish I had an exhaust brake - sure would help going down those long hills in lower gears - I have to be really careful in the mountains not to overspeed - I'm too old for white knuckle driving!
Greg

 

[Bob&Patty]

Brian, are we sure that the ABS is the issue or is the something keeping the rear brakes from working properly. Brakes will not work properly unless there is the proper pressure applied to all 4 wheels.

 

[brianharrison]

Hi Bob,

No, you are probably correct, the ABS is probably not the issue; however the EVBP may have been contributing to the problem. The fact Bill could not find a proportioning valve in his system bothered me hence I posted the excerpt from the service manual describing the operation of the brakes, including the ABS description and mode of operation. The EVBP uses the ABS components, as described above.

Bill is working with his mechanics (truck and trailer) and I'm sure will circle back with his resolution once he gets it figured out.....

Brian

 

[wdk450]

Here's an update on my rig braking situation:

While departing the Oroville, Ca. rally last Sunday, I tried stopping the rig at about 25 mph using the trailer brakes only. With the controller full on, full boost, I could feel some slowing, but I could not get the rig to stop. The trailer is currently at RV Dr. George who is seeing if my my frame flex might cause an incident while towing before I get to Elkhart for full repair, and fixing what needs to be fixed to get me there. He will also check out the braking system.

Meanwhile, I took the truck to a Brakemasters chain location here, and this time was told that the front disk system was O.K., but the rear disk system showed signs of overheating and excessive wear. New high-performance rotors ($200 each) and pads were installed, brake fluid was checked with a test strip, and due to the fact the floating rear axles had to be removed to replace the brake rotors (4 hours total labor), the out-the-door bill was $811 (after discount). The brake guys took it on 2 test drives before releasing it to me.

 

[Eddhuy]

Glad you finally found a problem that could finally fix the issue at hand but it makes you wonder. When I bought my Prowler last year, the service Tech that did the walk through said to do the trailer brake test at 20 MPH but I always do it much slower, guess I'll start doing the 20 MPH test, probably more meaningful than the slow test I always do.

 

[wdk450]

Glad you finally found a problem that could finally fix the issue at hand but it makes you wonder. When I bought my Prowler last year, the service Tech that did the walk through said to do the trailer brake test at 20 MPH but I always do it much slower, guess I'll start doing the 20 MPH test, probably more meaningful than the slow test I always do.

I looked up the manual for my Prodigy brake controller online last night that said to do the test at 25 mph, and set power wheel to a level just before trailer brake lockup. You might need a big parking lot and an observer for this adjustment. After the adjustment is done, while parked, enable your manual braking and record the numeric value. Then you can easily reset the power wheel to the correct value if you inadvertently move it during future driving.
According to the pictorial of typical rigs in the manual, a 5th wheel RV trailer/truck should be also set to the B2 or B3 boost modes.

 

[DW_Gray]

Hmm...

Bill, I don't know why the trailer brakes are not working correctly. Here's my experience from 2 years ago. After Lippert replaced my axles, including new drums and brakes, I was instructed how to get the self-adjusting brakes to adjust where they needed to. By the following morning on the way out of Goshen, I still had no trailer brakes. Concerned, I went back to Lippert. Fortunately, their brake man was there. After some testing, it was determined that the new brakes were so far out of adjustment, that the auto adjuster could not adjust. He manually adjusted them and I haven't had a problem since.

I've made it habit to test the trailer brakes occasionally.

 

[wdk450]

Dave (DW Gray):
After a harrowing, billowing smoke front truck brakes, descent of the Bighorn Mountains on Highway 16 on my way from Cody to Gillette last June, I had the Dexter factory rep at the national rally check and adjust my trailer brakes. He said that they looked fine. He didn't make any special comments about them being maladjusted. Based on that high level expertise report I believed that my trailer brakes were O.K.
My truck front disks and rotors had to be replaced at that time, though.

 

[DW_Gray]

Bill, just curious, did the rep jack up each wheel off the ground, rotate it and have you activate the brake controller to verify brakes stopped the rotation?

 

[wdk450]

"Bill, just curious, did the rep jack up each wheel off the ground, rotate it and have you activate the brake controller to verify brakes stopped the rotation?"

Nope, he just inspected the linings/drums and re-adjusted the shoe clearances. His time was pretty limited with so many rigs at the rally, and also running Dexter's vendor booth. I did tell him the Bighorn mountains story as why I wanted the brakes checked.

 

[DW_Gray]

Well, there you have it. I've adjusted brakes nearly all my life. I've never learned how to adjust brakes correctly without jacking the wheel off the ground. Sorry, but that rep did nothing for you. No wonder you have to replace the brakes on your truck so often.

 

[jnbhobe]

I agree with Dave, I've adjusted brakes all my life too and for the life of me I can't see how they can be adjusted right with the wheels on the ground !!!

 

[wdk450]

Dave and John:
To my memory the Dexter rep DID jack up the trailer (I can't remember if he removed the wheels - I was inside during the inspection/adjustment), and adjust the brake clearance. You have to at least rotate the wheels and note when they drag to do the brake adjustment. I remember him talking me through the procedure and talking about feeling the wheel drag as you rotated it, then backing off.

 

[Bob&Patty]

Dragging while turning??? How about tightening them until the tire wont turn and then backing them off until they drag. I guess I have been adjusting drum brakes all wrong for 50 years. Gee, I always thought that tightening "TIGHT" would center the shoes and get a better adjustment. Wrong again.

 

[jnbhobe]

Dragging while turning??? How about tightening them until the tire wont turn and then backing them off until they drag. I guess I have been adjusting drum brakes all wrong for 50 years. Gee, I always thought that tightening "TIGHT" would center the shoes and get a better adjustment. Wrong again.

I guess that makes two of us Bob, now I have to start all over, trying to teach an old dog new tricks.

 

[wdk450]

I most likely misstated what was told to me 12 months ago. With his 30 years of experience in trailer axles, brakes and suspensions, I'm sure he did it right.

 

[DW_Gray]

I most likely misstated what was told to me 12 months ago. With his 30 years of experience in trailer axles, brakes and suspensions, I'm sure he did it right.

Even so Bill, to not have your truck hooked up and actually test to ensure the brake controller was actually stopping the rotating wheel is kind of odd for man of that experience. (IMHO)