The rear brakes on my W250 keep locking up. Even on dry pavement. My dad bought it new the summer of '91, and as far as I know he had the same problems. The tires had flat spots with the steel belts showing when I bought it from him.

I replaced the MC as it was leaking when I got it home and other than locking up frequently, they seem to be in great shape. The pedal is very firm, not mushy at all. Could the ABS valve be bad? It never happens when I have a load in the bed of course. It can get pretty scary when running light on wet pavement though which happens a lot in Oregon.

The ABS light never comes on by the way, but the bulb is good.

Any ideas?

 

Check the anti lock module behind the glove box and see if it has been disconnected...Mark

 

Thanks. He did have a 5th wheel hitch and wiring installed when he bought it, so it is possible. What does it look like? Is it labeled?

 

The RWAL box is black plastic and is mounted just above the heater box. it's the only thing back there like that.
That in it's self won't cause the locking though.

 

Would it be something they might have done (common) when they wired in the trailer brakes?

 

Had a couple of girls run across a busy street (not in a crossing) and caused quite a few squealing tires. Caused my left rear to lock up and stayed that way for a few seconds even after I had released the pedal. The truck has about 78,900 on the odometer.

 

I would open the drums and look in the self adjusters.

Better yet. Try this first.... https://www.dieseltruckresource.com/...ctures-207170/

 

The black box is plugged in. So maybe mechanical then? Everything is fine of course when the truck is loaded.

 

Thanks. It has been a long time since I had to work on drum brakes.

 

You say thanks now Bwaaa Haaaaaa Haaaaaa, ...Mark

Read: these brakes can be a real female dog, but follow those adjusting instructions...

 

No, but it might have explained why the warning lights weren't coming on...Mark

 

Yeaper. I saw where you were going with that.

 

wheel seal rearend grease on the brakes

 

Good call, the old oil and grease causes brakes to grab, I forgot all about that...Mark

 

the dana 70 on these trucks have a oil cup in the hub that does not allow the oil to get on the shoes.