Posted prior 1997 ford f150 5.4L 4x4 front passenger side brake keeps locking/dragging I replaced master cylinder, rubber lines, calipers, pads, abs pump, pretty much everything besides the brake booster and it's STILL HAPPENING brakes are soft have to pump up then firm but by that time the brake mentioned above is LOCKED up I need some serious help from knowledgeable people PLEASE

 

Off hand I'd say you don't have things bleed properly.

Did you Bench bleed the master cylinder before installing? You have replaced everything else, why not the booster?

 

Brakes locking up after 10~ mins of driving usually means contaminated brake fluid. Moisture in the system will boil (expand) and lock down the brakes.


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Did not check into booster to see if any issues were there but doesn't the pedal usually get extremely hard when the booster starts to go ? And I bench bled the master with my mechanic (he's been a mechanic for 30+ yrs at a very reputable auto repair company) so I'm pretty sure everything was bled properly and procedure wise and how could I have contaminated the brake fluid ? I literally changed everything besides brake booster and steel lines so at one point the system was almost completely empty and I have refilled with proper NEW fluid

 

Also ONLY one brake is locking up like stated the front passenger all other brakes seem to be working just fine and I did replace caliper and pads but not rotors (never had just one brake lock up due to a rotor) it's just really odd that only one is locking up and did try another caliper so before we go there again same thing happened and I dont even have to drive it it can be on the lift and driver side tire freely spins and stops and releases when brakes are applied passenger side spins but when you hit the brakes it stops and locks up then after a few mintues 20+ it spins freely again

 

There is air in the system if you have a soft pedal and have to pump it up to get a solid pedal. Sometimes it is very hard to get all the air out. Did you lube the caliper on the sliding surfaces?

 

Yes I lubed everything and checked again to make sure nothing was hanging up and slides easily. Where could all this air be tho ??? I had the abs electronically bled by my mechanic several times we bled it to make sure but maybe there is air somewhere but I bled I believe 6 large bottles of brake fluid through the system did so much bleeding started to round off bleeder stems (purchased new ones have not installed yet)

 

Could there possibly be a vacuum leak ? And that is why I have to pump pedal to get hard ? Then after a few minutes the pedal returns to soft almost going to the floor....

 

I'm not sure, but, is there a separate proportion valve or is it built into the ABS? something is not letting the brake fluid to return. Considering you tried a different caliper with similar results...maybe you have a defective ABS??

 

I replaced abs unit and I'm hoping not cause it was a son of a gun to find one and if its the abs shouldn't or wouldn't the light come on ?? And I'm not sure the proportioning valve is inside the abs or somewhere else on the line what exactly should I look for ?

 

No idea Jake.. But, I did several pad/rotor brake jobs on my old 97 F150 and never had any issues.. All I ever did was just pull the calipers, replace pads, grease up the slid bolts, torque 'em down, done.. Same calipers for the 255,000 miles I put on it before I traded it..

I did bleed the lines each time, but never used more than a bottle at any one time.

Are the bleeder valves on TOP of the calipers? That can make a difference.

Good luck!

Mitch

 

If they aren't, you have the calipers on the wrong side - there's a left and a right caliper.

 

I did check that to make sure and when I did the calipers I went bought the driver side first then the passenger next day because I took off old passenger to inspect and it was beat up bad chunks and cracks I bought the truck with a break issue that was supposedly a bad abs replaced it and the calipers pads (not rotors) master cylinder and drum pads and hardware with wheel cylinders drove for a few weeks no real problems pulled to the right tho then had uper lower ball joints and inner outer tie rods done then an alignment 2 days later this brake locking up problem occured I did always have to pump the pedal once or twice to get firm but other then that and pulling to the right it never locked taking to master mechanic praying he can find out whas going on