jjf64

Hello to all,

Looking for info, if anyone else has had the same problem, of a 2500, diesel, with all brakes locking up. Vehicle sits most of time, for last few years, brake fluid is brown, but has been flushed and continuing to do til I get clear fluid.

Story is, driving in mountains, using brakes sparingly, when reached destination, smelled hot brakes. Figured it was because of the driving. On the way home, all four brakes would lock up. Had to stop, pour water on the calipers to cool them off, they were very hot, not red, but boiled the water on contact, and they would release. Only to do it again 20 miles down the road, then it kept getting shorter and shorter distances, before they would lock up again.

Another tidbit of info, I also removed the battery cables to reset the computer, thinking something might be wrong there. I never had any lights come on on the dash.

Finally, bled the drivers side rear, and all four released, drove fine for last 100 miles, then started doing it again.

So I'm flushing fluid through all lines, trying to get cleaned out, but wondering about the master cyclindar, if it's damaged, brake assist?, or other problem.

Thanks
JJF64

Humblecowboy

Yep, I'm going through the same issue with my 99 3500 ind suspension and rear drums. Drums aren't getting tight that I know of but the front calipers are. Rebuilt less than a year ago and recently they started getting tight again. I thought I had the system flushed good but there's a little crap in it and a little dark. Rebuilt calipers under warranty so they exchanged them without issue. Going to flush it good again before putting calipers on and see what that does. If same then I'm changing the combination valve and booster pump. My manual mentions "Self applying brakes" in the booster section but not sure if it means a gradual pressure. Please post back with whatever you find out.
I tried uploading the booster diagnostic page but it won't go. I'll try later

jjf64

Thanks, Humblecowboy,
I've flushed it, and it seems to have alleviated the problem, so far. Talked to another friend who said to take the caliper off, drain it and let it set for a day, making sure that it is cleaned out. He also mentioned getting "pin" (?) grease for it, he says it's at Autozone for $0.99. I haven't done this, but did blow out any dirt/sand that was there. Never got anything on the dash showing something wrong, so don't know if taking and getting codes printed out will do any good.

Thanks for the reply!
JJF64

Humblecowboy

I hope you have it fixed for good and I hope mine does too this time. I would love to blow the whole system out with air but I think that's a no-no for the ABS.
This is the link to the thread where I first posted it for the booster diagnosis. If mine start to tighten again then this will be my next process of elimination.

https://www.dieseltruckresource.com/...6&d=1406768795

jjf64

Thanks Humblecowboy, I meant, when I blew it out with air, the outside of the caliper, my apologies. I'm guessing the old fluid was my problem, I hope!! It was pretty nasty, but will check into your link! Thanks!!

jjf64

To anyone, Humble Cowboy as well, still having the problem of locking, but now only the RF. Again, bleeding the caliper opens it up, only to have it happen again.

Does anyone have any experience with the the combination valve? Can that be removed, drained and then bled out again? Noticed it has electronics attached, but never an ABS light coming on.

I've bled it many times only to have it lock up, again and again. So maybe the combo valve is sticking? How would one clean it out? Can it be cleaned out?

47Dodge

I wonder if you don't have some rubber lines going bad. Your new fluid gets dirty fast. I have seen wheels not releasing because the inside of the rubber brake line was bad and was loose inside creating a valve so to speak. You could force fluid to the brake (normal) pushing by the collapsed area and then when you released your brakes the fluid could not reverse and relax the brake.




47

.boB

Obviously, something is holding pressure in the caliper. As long as you have clean fluid in the caliper, continued bleeding won;t help you.

Next time it happens, loosen the connection at the MC. If there's pressure at that connection, the problem is the MC. If not, keep loosening each connection further along the line until find one that's under pressure. The problem is between that connection and the previous one.

jjf64

.boB, Thanks, yes very true. It's just the 2 lines going from the MC to the "combination" (or what ever they call it) valve box. then out to the calipers. I'm hoping that the flushing will remove anything between that line and the valves in the box? Correct me if my thinking is wrong. I've not seen anyone who has this part, if it is the problem. If it is backing up there, then the MC would be under pressure also? or would it just be that one line? Maybe I'm answering my own question, again, forgive me for not understanding what you've said? Please any more insight is greatly appreciated!!

torquefan

I've seen this happen several times after somebody has contaminated the brake fluid with the improper fluid, especially a petroleum-based oil, which causes all the rubber brake components to swell up. Essentially, the hoses will swell up internally until they seal themselves off and hold the brakes on. In this case, all brake components containing rubber must be replaced, and all steel lines flushed completely.

Take the lid off the master cylinder and look at the rubber seal on the bottom of the lid. It may be swelled up, deformed and gooey if the fluid has been contaminated.

jjf64

Thanks torquefan, I've only used regular dot3 fluid.

jjf64

.boB, I used to drive a chevy 6500, and had the same problem, but don't know what they did to fix it. Had a guy take off the top of the MC reservoir and there was pressure under neath the cap. The rubber liner is not gooey or distorted. My confusion is the 4 lines come into the combination or variable box, then to the 2 lines to the MC, so is it the MC or the line into the box then onto the MC? I'll see if it happens again, but if it does and there is pressure, how would one differentiate between the combo box and the MC?

.boB

If the MC is working like it should, there won't be any pressure between the MC and the combination valve. If there is, then the plunger in the MC is not releasing properly, and allowing the fluid to return to the reservoir. That would effect both fronts, both rears, or all four. But not just one wheel.

The only way there can be pressure in the reservoir is a blocked vent in the cap.

If the proportioning valve is blocked, it will create pressure behind it, between the valve and the wheel.

Each faulty component that is holding pressure will hold the pressure between it and the wheel. When you loosen a fitting and find pressure, then the fault is between that fitting and the MC. Since you just checked the previous fitting and there was no pressure, you've found your problem.

For example: Loosen the rubber brake hose at the chassis end. No pressure. Loosen the rubber brake hose, and there's pressure. The problem is between those two fittings, so replace the rubber brake hose.

Start at the MC end of the system. If you start at the caliper end, you'll immediately release pressure. Now you have to wait for it to happen again before you can check the next fitting.