I had a problem with my trucks brakes. The right rear tire would easily lock up when the brakes were applied, and the left rear was soon to follow. I don't know much about brakes and since i know someone, I took it to their shop. I had him adjust the brakes, and get them straight. They worked ok for a few days, and from backing up they re-adjusted themselves back to the way they used to be. Only now, both rear tires lock up very easily. My brake petal feels very high, and it requires a good amount of pressure to apply them. Even when you're stopped, it's hard to push the pedal down all the way, it kinda feels songy. It felt like this before he adjusted them, only now both rear tires will lock up (and ABS kicks in) and not much brake power is being applied to the front wheels. The truck doesn't stop worth of crap because of this. Now I do have a 6" lift and 35" tires, so I know the rear tires will want to lock up a little more then before, but not this much. I also realise that stopping 35" tires is a lot harder, but something just doesn't feel right in the pedal as well as the fact that the rear tires lock up too soon. Now that I know it's not an adjustment issue in the drums, what the heck else could it be? Brake booster? Proportioning valve?

 

Nobody?

 

Also looking for help with same issue. But my truck only does it on damp mornings. Dan

 

Possible causes (from the 96 shop manual, your 95 should be similar):
Damaged RABS valve reset switch
Leaky isolation valve
RABS sensor air gap too large
RABS sensor does not produce sufficient output
Damp or contaminated brake shoe linings
Stuck/leaking wheel cylinders
Rear brakes adjusted too tight
Hung-up parking brake
Hubs engaged although shift lever is in 4x2 position
Faulty 4x4 indicator light or short to 12V in 4x4 circuit 210
Stoplamp input to anti-lock ECM not present
Stoplamps inoperative.

The soft pedal can be:
Leaky dump valve
Leaky isolation valve
Stoplamps always on
Hydraulic leak
Air in system
Little or no vacuum boost
Stuck wheel cylinder
Pinched brake line

There's diagnostic routines for each of the above which are far too detailed to publish here. If you don't want to take it to a dealer, you'd be well advised to get a service manual CD off of eBay for your truck. They can usually be had for less than $20.

 

I used to have an old 1990 model that grabbed on damp days. A ford tech told me to take off the rear shoes and bevel the edges to 45 degrees and that would fix it. He told me that it used to be a fairly common problem. I was going to try it and see if it worked, but sold the truck. I never had any pedal issues though; mine always felt fine.
Just a thought

 

Sounds like something screwy in the booster, but the 4WABS should keep the rears from locking no matter what. Are the front disks contaminated with oil, or varnish? Are all 4 pads wearing evenly?

 

I'd say sensor problem

I have a problem with my right rear just staying engaged when i use the breaks. Though my wheel cylinder is not leaking.
However, it could be damamged.

 

The ABS kicks in and will not let the rear tires lock up now, but before..the passanger side rear would lock. Now that they were adjusted correctly, the rear tires just grab much harder than the front, and you can hear them skid when you stop (they won't completely lock but you can hear them squeak during the ABS function). Doesn't matter if it's damp or whatnot, weather does not really affect it.

 

Maybe they're just adjusted too tight!?!?

 

On earlier models, Ford had a problem with the wheel cylinders. They fixed the problem with new (improved) wheel cylinders but not sure if this is the problem on your '95. They are a cheap precaution that I would do anyway if your not sure if they have ever been replaced.

The hard brake pedal is what worries me. This is almost always caused be a vacuum leak. Check the hose from the booster to the intake. I would spray some starting fluid or carb cleaner on the hose (full length) and all over the booster itself. It could be the booster is leaking through the case.

You mentioned a spongy pedal. If the pedal goes down while holding the brake, you have air pockets in the hydraulic system. A simple bleeding of the brakes will usually fix this. If it doesn't, the booster or the master cylinder may be bad.

 

I guess spongy is a bad word..maybe springy? I don't think there is air in the system, and I don't think that the brakes are adjusted too tight. When I took the truck into the shop (I know the guy fairly well so he wouldn't rip me off) he adjusted them and it was marginally ok when I left, but after a few days the brakes adjusted themselves (from backing up and stopping) so it got tighter now, if I backed off the star wheels it'll feel better but, it just goes back after a few days.

 

No, there's nothing wrong with the adjustment. It's either in the hydrualic system or vacuum. I'm leaning towards vacuum.

I would check the vacuum line that feeds the booster from the upper intake. Spray it with starting fluid as well as the booster itself.

If that checks out okay, I would replace the wheel cylinders next.