2001 DRV 3500 5.9L

Been chasing down the cause of my front wheels getting too hot for months- new soft brake lines, calipers, disc pads, rotors, bearings and upper control arms. The lower ball joints were replaced about 15K miles ago and seem fine. The work is no loss as I'm rebuilding various systems for preventative maintenance purposes.

This has been a bilateral issue from the start and now I'm down to the master cylinder and the check valve on the booster. In cool weather I don't have a problem but hotter now I do.

My question to those of you with experience is which one of the parts mentioned would you think was more likely to be the problem?

Thanks in advance

 

Something is keeping pressure on the calipers... Usually, the first thing I think of is the soft lines.... but, as you have replaced those, *shouldn't* be the issue. Other things I have seen cause that, or dirty caliper pins/slides, or a misadjusted brake pedal.....

 

When you remove the master cylinder from the booster, you'll see a pushrod between the two. If the pushrod is too long, it will keep slight pressure on the brakes.

 

I had an issue, albeit in reverse of your issue, and the fix was to bypass the ABS pump using unions.

I had really weird brake issues - sticking, pulling and low pedal feel. This was caused by the pump.

I also replaced the calipers since at the time they were cheap -- this was about 7 years ago

 

Thanks to you all.

Besides the fact that I've already replaced some of the parts mentioned one thing I keep coming back to is that the problem is on both sides and has been from the start. That first time I didn't know what was going on and barely made it out of a long highway tunnel causing the front brakes to all but lock up. Also it seems significant to me that after waiting a couple hours for the very hot wheels to cool down I drove off and all was fine for months.

I do know that new parts can be defective but that's rare and for new parts to be defefective on both sides rare squared. That's why I'm looking "upstream" at the master cylinder and booster check valve.

I did take my van to a different mechanic, a "real" repair shop "Pep Boys" instead of the mobile mechanic I'd been using. Pro Boys drove the van a couple miles, put it up on s rack and without taking the wheels off tried to spin each wheel by hand. That was all. They told me my brakes were dragging and the wheels were hotter than they should be. That's exactly what I told them including the a list of which parts were new. There response was that all they could do was "start throwing parts at it " beginning with the soft lines and calipers. I walked, of course, and an employee came outside to tell me he thought it was the master cylinder although he had just heard his boss tell me the master cylinder checked out fine. I watched- they never lifted the hood.

I don't really mind replacing the master cylinder but that there is a booster check valve is new to me. Have you ever seen a bad check valve and could it be a cause for the fluid pressure not dropping after braking.

I'm pretty far down a rabbit hole already and just wondered now why the rear brakes weren't heating up also if it's either of the two parts I mentioned. Maybe when this is all done it might have cost less to refrigerate the brakes. (Bad joke)

thanks

 

The booster check valve ensures that you have some vacuum assist even after the engine stops running. That's all it does. Has nothing to do with line pressure.

 

Thanks,
New master cylinder coming up. You may or may not recall that I’m chasing down a “whirring” front wheel noise also. The noise is persistent enough in our high summer temps that I now can hear that it defiantly changes volume a bit in exact sync to the rotation speed of the wheels. In my mind it fits right in- it’s the disc pad too close rubbing the rotor. No brake drag or noise until driving a few miles and the parts heat up. I’m on the one yard line again, second down.

 

I *think* there is a spec for how far the little rod sticks out of the booster... May wanna check that as well.

 

How timely, you seem to have anticipated my Columbo style "Just one more question". Neither Hanes or the huge factory service manual for my exact model/engine DRV mentions that rod at all. Not under master cylinder remove/install or booster R/I. So I wouldn't know where to look for the rod spec.

The cylinder R/I looks easy enough and I think I'm gonna try and save the $400 to $500 I've been quoted and get my own hand dirty (something I always enjoyed) on this one. I should be able to get the flare nut wrench and bleed tubes easy enough which leaves the question of the rod.

For many 10 thousands of miles I never had this brake drag issue. Do these rods go out of adjustment after time? Anyway it may have been you but someone on this site spoke of adjusting that rod length a little bit- which direction to turn it and how much of a turn. They said I should be able to gain access to this rod without disconnecting the brake lines but just by unbolting the MC and pulling it forward a little bit. I will try that before before replacing the MC.

I'm all set up to run from a hurricane (S. FL) with solar, B2B charger, lithium batteries, generator and window unit 120v AC, oh- and a full twin bed. The only thing left I have to do is get the van running right.

 

It probably is just fine. I just tend to be a bit paranoid.

Having a second person to help bleed your brakes is the hot ticket. Borrow a neighbor kid if you have to.