This is a 6.4 l hemi 2500 HD. So no I don't have any of those components. I have fully and completely inspected the entire braking system. There's a lot of rubber lines a lot more than there used to be on older vehicles but the truck has 40,000 miles on it so I can't see that these lines are the culprit.
When I first took it to the dealership we thought it had air in it so they ABS bled it because I bled it and didn't get any air. They ABS bled actuated the valves it felt better until they shut the truck off. When they shut the truck off it all reverted right back to the way it was so it's not air. I've bled this system more times and I cared even admit. Including ABS bleeding it after I bought the scan tool. So I took it to a different dealer because they won't let me tow with a loaner vehicle. I explained the issue they went straight to replacing the ABS module. I don't even think that they did any real diag on it. The pedal was okay for the first four or five hours after the repair and then it reverted right back to doing what it's doing.
The service manager over there said he was going to do some digging and I gave him the name of this forum for him to research and then reach out to whoever because he was tossing around the idea that it could be an electrical issue. Which now I'm a firm believer of because of what I've already explained and they have known issues with the tipm.
At this point I'm at my wit's end and if the dealership can't fix it or they can't find it without having to keep my truck for a month or more I'm just going to wind up trading it. But to answer your question more directly yes after the hcu was replaced the master technician said that the master cylinder was the next thing on the list. I'm not really sure what list he's operating off of as there should have been some actual diagnosing going on. Rather that is looking at sensor data or using plugs to block off each hydraulic line until you get rid of this feel issue.
That is the one thing I have not done.
I noticed that the rear pads were spaced off of the rear rotors quite a bit so I had already ordered some rear calipers and they were not cheap. It did temporarily fix the issue when I collapse those calipers which in my mind I'm visualizing forcing the hydraulic fluid in the opposite direction which may have unstuck a sticky valve or something similar.
I was able to get it to do that same thing with the fronts. So we changed the master cylinder here with a buddy of mine and I put new rear calipers on it. The only thing the master cylinder fixed was the truck no longer feels like it's stopping with all fronts. It's more equally distributed but it definitely did not fix this excessively inconsistent pedal. I mean I'm literally driving it right now and every time I touch it it's doing something different and I'm not driving it any different and I'm hauling a 10,000 lb trailer. Every time I touch the brakes there's excessive travel and the trailer is being told to break hard because the truck thinks I'm breaking hard but in reality I have to go halfway down the pedal before I even get any hydraulic pressure so that's not normally either.
What the other guy said I'm half tempted to go pull that ABS fuse just to see if I can get a different feel. With the erratic sensor data taking the power away from it the valving won't maintain that pressure it'll default to something else that it's designed to default to when there's an issue with the system. But that's not a solution either and definitely should not have to pull fuses in order to make my brakes feel better.
