Front brakes locked up.

[gatorman21218]

So I just finished swapping in a rebuilt axle (DANA 50) that I bought from MUDKICKER. Well that was from an 85 truck, so naturally my calipers did not fit it. I bought reman-ed calipers and hardware from napa. I reused the brake pads because Napa had them listed for fitting all years.

I switched to hydro boost in the fall of 2010, using a remaned hydrobooster, a used F-SUPERDUTY MC and the pushrod. The brake pedal was modified to the correct pin height. Also at this time I replaced 95% of the metal lines and 1 wheel cylinder, along with all three brake hoses and new calipers (when they burned up the first time).

I drove it for the first time sunday to get it aligned and there were no problems. On monday I drove it to work (6 miles at 55 mph) and right as I pulled in the brakes were dragging. I opened up the driver caliper bleeder screw and fluid shot out and hit the fender well. I drove it home and had to stop (locked up again) and loosen it again just to get it home.

Last night I replaced both front brake hoses and drove to work this morning. Again it was fine all the way there but just as I pull in to park they drag a bit. didnt touch the truck all day. On the way home at about half way the brakes lock up. I hadnt touched the brakes in 2 1/2 miles. I was in second gear pushing 1200 degrees EGT and did that for a 1/4 mile just to get to the quickmart and off the highway. Damn brakes were on fire. luckily I had a fire extinguisher. So I got a ride home and got a plug and plugged off the forward port of the M/C. I drove home with rear brakes.

the brakes seem to only lock up when they are warmed up, and also apply by themselves with no warning.

Thoughts? I'm about to take 3 steps back and punt.

 

[bghnkinf350]

Might see if NAPA will give you a different caliper. If nothing else has changed except the caliper, then that is a good starting point, especially if it will be covered under warranty. Did you use new hardware? How was the wear on the pads? Even?

On second thought, this is a pressure problem - is there pressure on the rears? Is the booster pressurizing the fronts and rears? Do you have another master you can try out temporarily to eliminate that?

 

[gatorman21218]

Yes the rear is working. I plugged the front off and the rear works.

Is there a proportioning valve some where? I know there is that that ABS thing but that is only on the rear line.

 

[gatorman21218]

bump

 

[alienturtle]

how did you do the return for the hydroboost setup? A T or did you get the res with 2 nipples? If both calipers were on fire and hot then i would have a hard time thinking that 2 calipers are bad. Its possible but i think you have something going on with the booster.

 

[6 Nebraska IDIs]

I'm gonna put my .02 in as well. I had all kinds of brake problems, non hydroboost, a while back in my brown truck and it turned out the master cylinder was the culprit the whole time. Just took a few weeks to completely take a crap on me. Didn't do that thought until a shop had already changed the calipers and proportioning valve as well as the brake lines to the front calipers. I'd say you have a master cylinder issue.

 

[gatorman21218]

how did you do the return for the hydroboost setup? A T or did you get the res with 2 nipples? If both calipers were on fire and hot then i would have a hard time thinking that 2 calipers are bad. Its possible but i think you have something going on with the booster.

F-Superduty reservoir

 

[alienturtle]

F-Superduty reservoir

ok. I have heard that some people using a T for the return have issues with a restriction in the return side and causes the brakes to drag. Just an idea

 

[93f250idi]

Yes the rear is working. I plugged the front off and the rear works.

Is there a proportioning valve some where? I know there is that that ABS thing but that is only on the rear line.

there is a proportioning valve inside the driver side frame rail. you dont wanna have to buy one though. i priced one for my 93. it was a little over $500

 

[ADV]

the valve in the drivers side frame rail is the RABS valve. new at ford around 500 but a local parts store should be around 150.

 

[gatorman21218]

I dont see a proportioning valve on mine. There are two lines that come off the M/C. the front line goes to the driver side caliper hose and TEEs off and goes to the pass. side caliper. the other line goes down to the RABS thing and then back to the rear brakes.

Still my question is can a master cylinder go bad and hold pressure in the lines?

 

[Black dawg]

I dont see a proportioning valve on mine. There are two lines that come off the M/C. the front line goes to the driver side caliper hose and TEEs off and goes to the pass. side caliper. the other line goes down to the RABS thing and then back to the rear brakes.

Still my question is can a master cylinder go bad and hold pressure in the lines?

While the brakes are locked up, loosen the master from the booster and see what happens. I have seen one master cause brake drag.

 

[gatorman21218]

Well I bought a brand new master cylinder from NAPA. plan to put that on tomorrow when everything dries out.

Question: Does the rear ABS have any affect on the front?

 

[Black dawg]

Well I bought a brand new master cylinder from NAPA. plan to put that on tomorrow when everything dries out.

Question: Does the rear ABS have any affect on the front?

no affect on the front.

 

[93f250idi]

the valve in the drivers side frame rail is the RABS valve. new at ford around 500 but a local parts store should be around 150.

oh, local napa and orielys told me it was a dealer only item