f-350 rear brake locking up
 

I have a 85 f-350 4 door dually diesel. My problem is My one rear brake is locking up every time I use the brakes, after I let off the brakes it spins free. I put on a new master cylinder all new brakes and wheel cylinders and still have problem. Any ideas?

Nothing is messed up on the drums is it? My shoes on my truck got messed up last night from testing my E-brake (fail) and one shoe was demolished... Making noise using them and locking up when I was almost stopped, so take a look if you haven't yet. If it looks good, I would say the cylinder on the drums are bad. The part that pushes the shoes outward. I think its called the cylinder. Good luck.

He said he put new wheel cylinders in...

I've tried everything I can think of. My brake locks up right when you put the brakes on. The drums are good, no marks, no digs. The wheel cylinder is new but didn't help. tried loosening everything and it still does it. right now everything under the drum is new, It is only the right side, so I don't think it can be the rubber line. I am starting to think that I might make the other side do the same thing and enter some drifting comp's or rally races.

I have seen this happen when someone puts the two long shoes on one side, and the two short ones on the other side.

holy crap there is differant sizes? :-banghead

The long shoes go on the back side, right?

Oh, sorry. I missed that.

Yes, I believe that is correct.

yes, primary (short) shoe goes in front, secondary (long) in the back the shoes were never soaked with brake fluid or gear oil were they, that will cause lock up

Sorry if these are dumb questions..

Are the pins that transfer wheel cylinder effort to push the shoes out completely engaged in the shoes?

Were the bosses on the backing plate grooved or worn excessively?

Was the brake adjusted after your rebuild? Drum spins, light friction without brakes applied?

Adjuster facing the right way?

Do both shoes show evidence of touching the drum?

Does one shoe (primary or secondary) show more evidence of touching the drum? Might look closely at the top edge of friction material - closest to the anchor boss, or at the bottom, closest to the adjuster.

If one shoe is showing more evidence of wear than the other, it might lead you to what is happening.

The shoes did have some brake fluid on them from the leaking cylinder, but I didn't think it was enough to hurt them. I'll try new shoes.

Aha! That will fix your problem. Make sure to clean the brake drum really good too. When the shoes try to start drying out, they start to get gummy and will grab.

Can I just clean with brakes with cleaner or are they shoot. Thanks for all the help.

Cleaner won't work. They are like a sponge and are soaked. Each time they get hot the old fluid is going to seep out. Believe me I am a penny pincher myself, but have never been able to get brake fluid out of the shoes and pads.

Sometimes on equipment that has to be running and we don't have the parts in stock, I have taken a torch and played the flame over the shoes to burn the oil out of oil soaked shoes. But this is just a temp solution in a crises.