brake drag

In my discussion above I put I replaced all the brake cylinders but what I meant was I replaced all the calipers. Alberts

As your pads wear, the caliper moves on the caliper mounting bosses to allow for reduced pad thickness. The piston moves out of it's bore to compensate for wear. The caliper starts out in one position when pads are new and moves in relation to the centerline of the rotor as they wear.

Check to be sure that there is no binding at these mounting points. You should be able to move the caliper back and forth (without rotors) about 3/8" perpendicular to rotor face.

bobc, and others, could provide more enlightened explanations and fixes.

The free play travel adjustment in the brake pedal can cause the build up of brake pressure if the master cylinder is not allowed to return to the "at rest" position. To test for this, drive the truck for a distance that would cause the brakes to drag and become hot. At that time go to the front wheel caliper bleeder valve. Open the bleeder. If fluid is under pressure, something is holding that pressure, and not venting it back into the master cylinder. Check a back caliper also.

The things that could cause this problem are the free play in the master cylinder adjusted to tight until it holds the master from returning to "at rest " position.

Possibility #2 is a bad rubber brake hose that is acting as a check valve. This would likely only affect one wheel, or two, as brake hoses failing this way are rare, and it would require one for each front wheel, and a third for the rear wheels. This seems unlikely to happen to all three hoses at once.

My third guess would be the anti-lock brake controller. I have never heard of this, but would not say it could not happen.

The last suggestion is to question weather your brake system has had petroleum based fluid added to it. You stated that you replaced all brake calipers, but not why. Has your rubber master cylinder cover gasket swollen up ever? Oil contamination of the brake system will require replacement of all of the rubber components. The brake fluid will mix with the petroleum based fluid, and damage rubber components far away.

I hope this helps. Good luck.

this is what I would do first. Go out and drive around a bit, or until it starts to squeak again, you did put brake grease on the shoes didn't you.

Now turn the truck off and open the hood. Pull out the hos on the vacuum brake booster, nothing should happen.

With the motor off there should be no vacuum, if there is you have narrowed down the search.

I use anti-seize on the back of the brake pads when I change mine.

good luck

The one answer is fairly correct....you should have what we call bleed back into the master cylinder when the brake pedal is at rest. I do remember reading that all disc brakes require 10lbs of pressure to allow for the adjustment factor mentioned. There is also something called a proportioning valve that puts more pressure on the front brakes than on the back if you have disc/drum combination. If it were my truck I would start with the bleed back factor. I know you can check this if you have someone depress the pedal then release it. About a second later you will see a little "geyser" inside the master cylinder on most vehicles.....that would be the bleed back. If the fluid is full, you may just see a little bit of a "bump" in the fluid when it bleeds back....still an indication all is well. If you don't have that, you could very well be pumping up the brakes and not releasing all of the fluid back into the master cylinder. In that case, as mentioned, you need to adjust the free play in the pedal, usually from under the dash inside the truck but sometimes you need to pull the master cylinder to reach the adjustment rod. I would also check the antilock brakes, but make that a last resort since the $ factor can become hurtfull on that one.

Say, you wouldn't be one of those idiots that drive around with your left foot on the brake would you? Saw your left leg off at the knee should do it...

Firstly, did you clean everything properly, or just force the pistons back and put new brake pads in? The rubber seals must be free enough to "lift" the pads off the disk when brake pressure is zero....if very dirty, this may not function.

Is there anything preventing the brake pedal from returning 100%....or is there dirt in the fluid? Has the fluid been replaced in the last 24 months.....?

The foot resting on the pedal would also do it!!! as already mentioned elsewhere....

Just finished up a big brake overhaul on my own F250. From all the work and all of the previous postings there are not many options open to you. If all four wheels are getting hot from drag then you must have significant residual brake system pressure.

So the next question is were your brakes doing this before the overhaul? Brake fluid must move freely into and out of the master cylinder. Back in the day disc/drum and drum/drum systems used a residual pressure check valve for the drum(s) half of the system but the disc needed no such device. Observing the return of the brake fluid has already been noted. If you can't see a "fountain" I would really lean into a new master cylinder.

As a final check get upside down and really look to make sure nothing is interfering with your brake pedal linkage.

Happy Camping!

Wish I would have seen this sooner!

http://www.prenhall.com/autoweb/techtips/brakes.html

Nice article, and a good answer. The drip test will not test for bad hoses, but it brings us closer. Thanks for the link.

Many times, in fact, more often than not, the booster (sometimes called a hydravac unit, depending on the application) will start to deteriorate in the diaphragm; this allows brake pressure to be applied to the master cylinder as you drive. For several years Ford had trouble with these units on their F600 series trucks, and you would have to stop the truck, bleed the built up pressure off of the booster and then proceed on until the next time.

Make sure that you have no existing pressure on your system, then start the truck and just sit their and pump the brake slowly and notice if the brake pedal seems to build up on you (stroke distance gets shorter); this will tell you what is going on.

oldgolfer

Hello there

The problem of brake drag can usually be traced to a blocked compensating port in the master cylinder or lack of slack in the brake pedal rod between the pedal and the master cylinder. If the rod adjustment is incorrect it can push the piston in the master cylinder forward which then with seal the small compensating port. This will prevent the brake fluid from returning to the master cylinder once the pedal is released after braking.

Hope this will help. Chris de Weerdt, South Africa