I put in emails and calls to both a local Ram dealer and Mopar Overstock.

Crickets.......

I have heard that these units are NLA from other sites. So that makes sense.

I did find a rebuilder of these HCU's.
I have one coming and should be here in a few days. I did not want to send in my original unit as a core. In fact, on these 1998-2005 models, they dont even want them. So, I will need to mount my original Module on the HCU when it arrives.

Just good to know for any who don't. There are two parts to these ABS units.
1. Electronic Module
2. HCU (Hydraulic Control Unit)

That HCU nomenclature is paramount when looking for these. Valve Body does not cut it!

So, right now this is where I stand with parts.

1. Original, complete ABS unit with working Module and semi-bad HCU. Works with a soft brake pedal feel. On the bench.

1. Junkyard, numbers matching ABS unit with working Module and semi-bad HCU. Works with a soft brake pedal feel. Installed in working truck.

1. Remanufactured HCU coming from rebuilder.

I will place my original Module on the rebuilt HCU and install. Bleed again for the 1,000,001 time and post the results here.

Also, as time allows (which is never) I plan to open up the Junkyard HCU. How hard can it be in there?
O-rings? Seals? Can't be that hard. Hell, it just may be crap inside there and needs a cleaning.

I also found a technical bulletin on this era of Kelsey Hayes ABS units.
It stated that when this spongey pedal feel happens that the HCU is leaking internally and the brake fluid will return to the master cylinder. So that explains a lot. Because something is giving in the hydraulics. No leaks anywhere. But bypassing and giving. Been a maddening experience!

I will report back!

Thanks!

 

HCU is likely just like the MC, using cyl/ipistons with rubber seals. I haven't pulled one apart yet, so I'm curious to see what they look like... please post pics! :-)

 

Wonder if you can get rebuild kits for them......

 

I will post back with my results. Both with the hopeful success of the rebuilt HCU and a excellent brake pedal feel.

And if I have some time, photos of me taking apart the Junkyard HCU.

✔️👍💪

 

OK,
I have received the "rebuilt" HCU.
I do not feel that the unit I received has been rebuilt.
Rather, it's a tested unit out of a truck that passed.
It comes with a one year warranty against failure.
I am OK with that. As long as the supplied HCU works as it should.

I have mounted my original ABS module on the received HCU. It is ready to go into the truck and be bled.

If that spongey pedal is still there after this.........
🤦

I will report back.

 

Well, I wish I had better news.
This so-called rebuilt HCU is a bust!
The pedal goes right to the floor.
Worse than ever. I should have let well enough alone. The local junkyard replacemet was woking OK, just not as firm as I wanted it.

This "Rebuilt" unit is as bad as the original when I bought the truck. One of the reasons I got a big chunk of change off this truck was because of the mush brake pedal.

So this "Rebuilder" says to send it back for either another one or my money back.

I am going to put the local junkyard unit back in and at least get back to where I was. A running truck with a pedal that I feel is 85% right.

I know others have solved this problem with a new HCU. But for me it's been Unobtainium!

I am going to open up my original HCU and see what I see next.

🤦🤦🤦🤦🤦🤦🤦🤦🤦🤦🤦🤦🤦🤦🤦🤦💩

 

Original ABS brake lines cut to short nipple adapters.

Clear vinyl tubing attached to nipple adapters and run into brake fluid reservoir. Submerged into fluid.

 

With this setup, I have been pressing the brake pedal down many, many times to purge the air. Then when tubing was clear of bubbles, I ran the ABS bleed with scanner multiple times. Then more brake pedal action. More ABS. Over and over until finally, no more air bubbles. I am also letting it sit for a while and then going to do it again.

Then, as quick as I can, hook up the trucks brake lines and run a four corners bleed. The lines and calipers are are ready free of air. So there should be really nothing to bleed out.

After this I am living with it.
And to be clear, the Local Junkyard ABS/HCU is back in the truck.

I have high hopes on this ultimate setup working.
I have done full overhauls on brake systems with ABS before. And NONE of this was necessary.
It sure is on this 2005 era Kelsey Hayes ABS.

I will report back on final results.

 

Final results are in.

Brakes are OK. Back to where I had them. Maybe a touch better. I would say 90% of where I would be satisfied.
There is zero air in the system.
Brake pedal feel is OK. I am not going to say great.
Old Kelsey Hayes literature says that with this system some brake pedal feel is sacrificed for the safety of having antilock breaks.

Maybe a new HCU would get that last bit of feel back. But I doubt it. Plus, can't get one anyway.

So, to anyone out there that reads this long saga:

If brake pedal goes to floor, barring all the other obvious things, the HCU is shot.
If you have checked everything or replaced eveything and bled the system to the point of exhaustion, and the pedal is OK but is a bit soft feeling. That's all folks! Nothing more to do.
Other than upgrade to the stainless braided hoses.

It's as good as this system gets.
Remember too that this is a 2500 HD truck.
4WAL disk brakes.

Hope this can help someone on here.

 

That is quite a saga. I have a 2007 2500 4x4 with about 190k miles. I have a spongy feeling pedal. Exactly the same as what you described. I recently replaced the right rear caliper and did a 4 corner bleed just to be safe. It is still spongy. I think I'll just leave it alone since the truck stops fine and I have so many other projects to deal with right now.

My wife recently drove the truck, after the repair, because I was working on her regular vehicle. She called me from the road saying the pedal went all the way to the floor and felt soft. She got home and I went for a test drive and was like, what are you talking about? It's always been like that. I did have the brake line going to the back rupture a while ago. Maybe 4 years ago. I had someone else repair it as it was winter time and I don't have a garage and my hands can't tolerate the cold. I can not remember if the pedal feel changed at that point.