I smelled that signature "your brakes are on fire" smell, so I went around looking for the one with the problem. Only the driver's side front was hot so I went about bleeding it thinking that some air in the lines might be holding a residual pressure on the caliper and causing the problem. Not so, so the next idea was the caliper was sticking. I replaced it and the flexible line for good measure, and it still sticks. I can't even rotate the rotor with my hands it's stuck so bad. As of now I'm thinking master cylinder or distribution block, but any ideas would be much appreciated.

oh yeah this is a front disk/ rear drum manual brake system.

 

Air in the lines will not cause residual pressure. I too was thinking stuck caliper while reading the post. Check the hard lines for a pinched or crushed spot. Also check that the brake pedal is returning all the way up. Maybe the linkage between the pedal and the MC is binding. You might try pumping the pedal a couple of times and then with no pressure on the pedal, crack open the bleeder valve and see if the fluid is still under pressure. Knowing that will help isolate a hydraulic problem or a bad remanufactured caliper.

 

Bad wheel bearings can cause that also.

 

Raise and block wheel. Remove caliper, and rotate rotor. Does rotor turn freely. It seems like no or very minimal grease on bearings. Also check inner axle bearing on spindle.

 

I'm putting my money on bearings.

 

yeah the caliper rotates well without the caliper on, but thanks for the lead. It even rotated well once I put on the new caliper, it's when I pressurized the system and bled it that the caliper started grabbing again. Thanks for the help so far, and keep it comin' . I'm gonna go try your suggestion 76supercab2, and I'll get back to you in a few minutes.

 

alright 76, here's what I did.

I got in and pumped the brakes about half a dozen times, then cracked trhe bleeder. The fluid kinda dribbled out, not really shooting out like if I had another man bleeding. I don't think that this has to do with the hydraulics, due to the whole siphoning that the fluid can do, but am I wrong? Anyway I hope this and the other stuff I said help out a little.

 

yeah and I should have clarifyed in the original post that I know it's the brakes messing up 'cause you can see that the rotors got really hot when I smelled them burning. That metal coloration you see on some motorcycle exhaust pipes was on the rotors. It's kinda hard to describe but I think you get my meaning.

 

Curious.

So the caliper is a free floating design with a spring loaded keeper on the bottom edge - held in place with a 3/8 bolt. Right?

Is it possible the caliper is sticking? It should move fairly freely with piston pushed back into the caliper housing.

Is it possible that the other side is not braking at all? All the braking on one side will really heat up the rotor and pads, then things start getting worse from overheat.

Assume you have the caliper on with the bleed nipple at the top. Assume also the pads are correct and rotors are correct.

Keep the diagnostics coming. Very interesting problem.

 

alright tinkerer, you're right on the money with the caliper design, the keeper or keeway on the bottom, 3/8 bolt to hold it in place, and the bleeder nipple on the top. Free floating design. I'm not sure on the other side's caliper, I haven't checked it as of yet, but I really should because this seems to be more than a localized problem.

I think that the right brakes might tell may have someting to do with this as the truck used to pull right when you stomped on the brakes, the harder you stepped, the harder it pulled. I thought it was just air in the lines, but now I'm not sure.

The caliper is a newly rebuilt one from advanced auto. Saying this it may be a bad rebuild, but for now I'm trying to think of something else. The pads and rotor weren't doing this for months before, so I think we can rule those out as well. But like you said it's quite perplexing. I also replaced the flexible lines, if that had anything to do with it.

 

internal damage to the brake hose can cause this problem too.

 

were any other brake system parts replaced?

I'm thinking the rod on the power booster, behind the master cylinder, the push rod could be to far out. Check the power booster push rod, the push rod screw to power booster unit should have a clearance of 0.980 inch to 0.995 inch.

How the brake pressure at the master cylinder lines?

 

You got my Haynes Manual out for this one.

I think it's really odd that only one side is showing overheating. According to my book, the system is split between front and rear axles. If there is a pressure problem on one side, it should be evident on the other side as well.

The fact that it used to pull to the right indicates that the right side was braking more than the left. Does it pull either direction now? Have you checked the rear brakes? The front brakes do most of the work. If the rears fade, it would make the front brakes work/heat up more. It's easy to overlook until you lock up one set and get nothing from the other.

OK, I have to ask the simple question: When you changed the caliper and hose on one side, did you bleed both sides? I'm not happy untill I have fresh fluid throughout the system. For that much grief I prefer to cover all the bases and be done with it.

I learned something new tonight. The book says that "On vehicles with disc brakes, a bleeder rod located on the pressure differential valve must be released to allow fluid to the front calipers." according to this book, you can hold the rod out (under 6800 lbs gross. If over, hold the rod in)with vise grips while you bleed the system.

Oh yeah, the book says that if you open any part of the system, bleed the entire system. Looks like my fetish for changing fluid payed off, otherwise I would have been wrong all these years. LOL

If you don't have a manual to refer to, send an email. I'll scan the relevant info and mail it back.

 

1975 ford, that sounds like a thing that affects the power brakes, I have a manual set, would the clearance of the parts behind the booster be a problem there? I ahaven't replaced anything other than pads on the front brakes. Checked the rears a few months ago, not enough wear to constitute replacement.

Hypoid, I think you gave me some stuff to deal with here, I didn't know about the pressure differential valve. This may be the problem. I'm gonna bleed the other side and mess with that valve, hopefully taday, so keep your fingers crossed. oh, and the gross stuf refers to the truck weight and not line pressure I'm assuming.

I haven't driven the truck since I started this work as I don't want to do any more damage to the rotors.

 

ok update. I really should have done this in the first place but it seems that the other side is locked up as well. I'm gonna try to bleed the excess pressure off of the other side and see if it makes any difference on the lockup. As of right now I'm thinking master cylinder, any suggestions?