Had a front caliper locking up on my way home. Changed both front calipers and bled all 4. Changed all rotors and pads in the fall. Now after driving approximately 5 miles all 4 slowly locking up. Possibly master cylinder not releasing? I tried turning in the booster rod but no change.

 

how do you know all 4 are locking up? are they all 4 crazy hot when you stop?

Had you previously modified your booster output rod?
What made you think to adjust that?

Have you ever changed your master cylinder?

 

All 4 smoking. Did adjust rod several years ago. Master never changed. 259,000 on truck.

 

As I suspected... and as I warned repeatedly in the thread that mis-advised everyone to adjust their vacuum booster output rods.

Most likely you have always been trapping pressure, but a less-than-ideal bleed and maybe lower friction pads didn't cause problems.
Maybe your old rotors had some small warpage that pushed the caliper pistons back and avoided dragging.
(my best guess is that you were trapping a small amount of pressure but the air in the system "hid" the pressure so the brakes didn't drag)

Anyway, now that you have a freshly bled system, with fairly new rotors and pads, you are trapping more pressure.
This means the brakes drag slightly, and start to get warm. The hotter they get, the hotter the brake fluid in your calipers gets. Hot fluid expands... thereby further increasing the pressure and compounding the problem.

I'm guessing your booster output rod is still too far out, even after you tried adjusting it back in.

The proper way to fix it would be to find a shop that has a special gauge to measure the length and adjust it properly.
The quick/cheap method is to keep adjusting it in until the problem goes away.

You could also replace the vacuum booster, with the assumption that the new one would come with the proper output rod setting.

(BTW - I have been working in the brake industry for 12 years now. These are facts, not wild guesses)

 

It could also be the MC but if you have been dorking with the booster, that would be a good place to start.

 

I have had the new rotors and pads since october. With 5-6000 miles on them. And just 2 days ago the fronts were only locking up. Now with new calipers in front, all 4 locking up. They are fine, until the more i acuate the brake, the less the pedal goes down until they start dragging.

 

Check the flex lines on the front, perhaps they are twisted if caliper(s) were rotated 360

 

yes but all for are locking up.

 

I didn't have a chance to look at it today at work. I had to work 6 to 6 today and they closed up shop at 6. So I drove the bosses truck home today. Might get a chance tomorrow.

 

then I guess check booster rod as suggested a few replies up^^ Oh I see you already did that.

 

it is extremely unlikely (pretty much impossible) that the MC would be trapping pressure in both circuits due to an issue within the master cylinder.

 

Hey I'm having same issues except mine is a 1997 5.4 4x4 front passenger side brake keeps locking up and I replaced rubber lines and the caliper still dragging and locking up HELP!!!!!! I belive master cylinder is the culprit buy why would it only lock up on one side I was told my master was bad and needed replacing

 

Take another look at the caliper and make sure it's installed correcty and the sliders are properly lubed.

 

I have taken them off and made sure everything was properly greased and I forgot to mention I just hand upper and lower ball joints replaced along with inner and outer tie rods then had an alignment done and now the breaks lock up I bought the truck because it had bad abs unit sooo I replaced bad abs unit had it electronically bled I replaced a ton so far new drum shoes and wheel cylinders and sprung kit replaced both front calipers and rubber lines and the pads and the master cyliner then had all that other work mentioned above done and now tonight I'm pulling up my road brakes are smoking passenger side front damn near caught fire PLEASE HELP (I had brakes working fine little soft but worked fine before I had all this steering and other work done)

 

Could that new caliper be sticking?