I am just about at my wits' end over a brake problem I'm having. I'm really REALLY hoping someone here can help me out.

Apologies in advance for the long post -- but I want to get all of the facts on the table.

Here's the deal:
* Drive the truck after it's been sitting a while (overnight, or at least a couple of hours), everything's fine. Good brake pedal feel.

* Drive 10-15 miles, stop-and-go at lights and stop signs, the brake pedal slowly starts to feel firm. Then very firm. Then, no play whatsoever. And brakes are dragging bad. Tonight, they were dragging so bad that I had it pulled into 1st gear with pedal on the floor just to get thru an intersection.

* Get out and check each wheel, all 4 brakes are dragging. I can tell from the heat pouring out of each wheel. And I've verified with infrared thermometer. Also, I've raised the vehicle when this is happening, and all 4 wheels will not turn. So it's definitely all 4 brakes.

At first, I assumed it was the infamous seized slide pins. But I've THOROUGHLY cleaned each and every one, and lubed with synthetic caliper grease. When the brakes are feeling normal, I've had my wife pump the brakes while I watched the calipers. Near as I can tell, they slide easily. Again, when my problem happens, it's all 4 wheels SIMULTANEOUSLY. So I've pretty much ruled out slide pins.

The brake pedal itself isn't getting bound by anything. It moves freely and I've lubed each of the pivot points. No problems there.

When the brakes are dragging, I can crack the bleed screw and some fluid will come out at each wheel, which releases the brake at that wheel and I can then turn each wheel freely. So, residual pressure in the lines. I replaced the master cylinder (twice actually). No change in behavior.

BTW: I thoroughly bled the lines after each of the two master cylinder changes. I must've put 60+ ounces of fresh/clean/new fluid into the system.

Next, when the brakes are dragging, I can unscrew the master cylinder a bit from the booster, and the brakes immediately release. Again, residual pressure in the lines. So, I assume that something funky is going on with the brake booster. Also, when the brakes are dragging, I can pull the vacuum hose from the brake booster. And after a few seconds the brakes release. So I install a new brake booster. No change in behavior.

After swapping the brake booster, I can still pull the vacuum hose when the brakes are dragging and it'll release in just a few seconds. So, it really seems like something is going on with the booster, but I can't figure out what it might be.

New master cylinder and new brake booster, both within 2 days, and no change. Brakes still drag.

So...WTF?? Anyone have any ideas or advice for me?
I'm off to get another beer, I need it....
If someone can help me figure this out, I'll gladly send you a case of your favorite beverage. Or, at the very least, wire the funds to pay for a case.

 

There is a release valve inside the master cylinder and your's would seem to be sticking, the resulting being brake pressure not being reduced when brake pedal is released.

Time for a new master cylinder. Get a good brand not the cheapies, bench bleed it properly then install. After installation bleed all four calipers or cylinders once again. That should solve your problems.

 

Both of the master cylinders that I've tried have been brand new (NOT re-manufactured) units from NAPA. But I'm just about willing to try anything.

Maybe there's an air bubble inside that somehow didn't get purged, and that's screwing up the release valve? I'll pull this latest one from my truck, which is all of about 4 days old, and re-bench bleed again. If that doesn't work, I'll go back to NAPA when the brakes are dragging, show them what's happening, and ask for yet another one.

I truly appreciate the input. But...how would a faulty release valve in the master cylinder explain the fact that I can pull the vacuum hose from the booster, and the brakes will release?

 

I pulled my 4-day-old master cylinder tonight, and re-did the bench bleed. I didn't see any bubbles.

Re-installed, took it for a ~15min drive, brakes are dragging.

Pull it in the garage, lift the vehicle -- all 4 wheels are dragging.

Open the hood, loosen master cylinder from the brake booster via those 2 14mm nuts about 1/8-inch -- brakes release.

If it were the master cylinder, loosening it from the brake booster should have no impact (right?).

So I'm back to suspecting it's the brake booster or something therein related.

It is possible for the brake booster vacuum tube to have TOO MUCH vacuum, thereby causing the brakes to be unknowingly applied? Is there maybe a regulating valve of some kind in the line?

 

Well at this point with your testing and such it all narrows down to the booster chamber---maybe. Its quite possible an internal failure causes the diaphragm to keep pressure on the MC piston, releasing the vacuum allowing that part to "relax" and relieve the pressure on the brake cylinders/calipers.

Was the booster a good quality part or something else? I'm assuming there's a warranty of some sort so maybe time to swap it out with another unit.

I'm assuming prior to this brake issue there wasn't a collision of any sort, something that might have moved the booster & MC even a small bit? I've known the brake pedal rod leading into the booster to be out of adjustment causing similar problems.

You might also post this in the Brakes sub-forum---this is mostly for the V10 Modular Motors.

Sorry I can't be any more helpful than this.

 

The new booster also came from NAPA, and I believe it is a re-manufactured one -- it's all they had. It did come with a lifetime warranty, so I should be able to return it. Especially if I can pull into their parking lot with dragging brakes and demonstrate to them that they will release with: a) slightly loosening the nuts for the master cylinder; b) removing vacuum line to the booster.

I've owned the rig for almost 4 years now, and it's never exhibited this behavior previously. No wrecks or anything like that.

I was not aware there was a Brakes sub-group -- thanks very much for pointing that out! I posted in the V10 forum only because gasoline engines use engine manifold vacuum for the booster. I'll definitely post it up in the Brakes group.

 

It did this BEFORE you changed the master cylinder?

The "release valve" in the master cylinder is just a port in the cylinder that allows pressure to return back to the reservoir. If the pin from the booster is adjusted out too far, the pressure will never return back to the reservoir and they will eventually get fully pumped up.

When you pull the master cylinder out from the booster, is vacuum escaping?

 

I changed the master cylinder the first time about 7 or 8 months ago. At that time, the brakes were starting to feel a little squishy and soft. The new master cylinder last fall made them feel better. It drove absolutely fine for the past 6 months or so. The dragging brakes issue has been something that started happening only in the past 2-3 weeks.

That's a good point about the pin possibly being adjusted too far out. I'll take some measurements regarding its current setting vs depth of the slot of the master cylinder. And I'll adjust it back and forth some to see if that has any impact. But, again, if removal of the vacuum tube from the booster fixes the issue (at least temporarily) - that is, doing so releases the dragging brakes - wouldn't this be indicative of a problem within the booster itself?

When I loosen the master cylinder from the booster, there is not any vacuum escaping. At least none that I can hear.

 

Yeah, that does sound like the booster doing something wrong.

There is a one-way valve in the hose where it plugs into the booster. Is this a restrictor of some sort? I haven't had anything to do with that stuff on my modern vehicles, so I'm not sure if it's a restrictor, and/or just a one-way valve to keep vacuum in the booster.

But I wouldn't think that would cause this problem either.

Maybe the old booster was sticking, and the pin wasn't retracting all the way. You replaced the booster, but didn't adjust the pin correctly, so now the NEW booster behaves just like the old one and won't allow the master cylinder to come back all the way. ???

Maybe?

 

Definitely a "maybe". I'll adjust the pin and see if that has any impact.

Really appreciate the input!

 

Finally had a chance to do some more work on the truck yesterday.

Through some careful measurements with digital calipers, I determined that the adjustable pin on the new booster was extended too far out by about 1 thread (1 complete turn). I did my best to match the extension of the new booster to that of the old one. But that wasn't apparently good enough.

After the above adjustment, I was able to drive the rig almost 100 miles running errands in town and the brakes never dragged once. I assumed a mis-adjusted pin would cause the brakes to drag on the first brake application and not something that would show up after 10-15min of driving. I am a very happy guy again.

Thank you, Art, for suggesting the adjustable pin!

 

I have a 2000 f250 and the brakes were a pain in the ***.

First I had warped rotors up front. Replaced those and pads on all 4 corners.

Then a piston crack in right rear caliper. Replaced that.

Front left starts dragging and binding. Replace both front calipers.

Right rear dragging and binding. I replaced both rear calipers(the one was warrantied) and rotors and the master cylinder for good measure.

That was all in about 6 months.

She stops good now. Lol.

 

Hey TruckFella

I am having the very same problem, Dragging all 4 dragging brakes.

Did you have any more issues with yours. I have not replaced the master or booster but I owned my 05 250 SD about 2 years and have only put about 8g miles on it. It may have been replaced before. ANy Tips or tricks you have learned for testing this other then mentioned, I am going ti try get them to stick it seems to happen when it is hotter outside or more when you have to use the brakes a lot in the last few minutes. Kind of lke pumping them up. I would et for 15 min and then they were OK but somtimes 2 of them would release on there own and not all of them.

Glad to find this post giives me something to go by.

​​​​​​​Tom

 

Nope, never had any additional problems since my latest post above.

I've since installed EBC Yellow Stuff brake pads and WOW do those things bite! Definitely a step up (or a few steps up) from the OEM pads that were on there previously. If I step on the pedal hard, I can lock all 4 tires. My stock pads never performed like that. Be advised, the Yellow Stuff pads do generate a lot of dust, and they squeal on a regular basis. The squealing could likely be addressed with copious amounts of caliper grease on the pads. But I've been too lazy to get that done. It's not my daily driver either so I don't think about it often.

Hope this helps.

 

I believe that the problem is the adjustment of the rod that go's between the master cylinder and the brake booster. It needs to be shorter