APD

Whenever I leave the house for the first time in the morning, my rear brakes grab really hard or even briefly lock up, the first one or two times I apply the brakes at the closest stop sign to my house.
Brakes are fine all day after that, but they always grab the first time I use them in the morning.
Could this be an ABS thing?
Any ideas of what would cause this?

wannadiesel

Two things spring to mind:
Surface rust on the drums.
Leaky hub seals.

APD

I had the drums turned last time I did the brakes (~ a year ago), and its my daily driver, so I cant imagine much rust build up.
How would leaky hub seals cause brakes to lock?
I did replace the hub seals when I did the brakes last year.

dillenger1

do you have hydroboost?Why would a gear oil on the drum cause it to grab?it would do the opposite.Theres a propotioning valve under the driverside of the cab that controls this.Did anything get messed with?

sdstriper

I would get under there and manually adjust the rear brakes. Commonly overlooked procedure.

Power Ram 250 C

If it is wet out on a morning or it is just wet out, mine will do the exact same thing. You can even feel the RWAL try to work like it should when you barely hit the brakes.

ebteckx

Believe it or not another thing that can cause that is water in the brake fluid... can rust up wheel cylinders... I know it sounds strange but I have had it happen...

93John

If any type of oil/brake fluid gets soaked into the brake linings it will cause more friction and cause them to stick.
When the axle bearing went out on my service truck, it leaked oil, causing the brakes to lock up the first couple times stopping. Then was fine after that. It leaked for about 3 weeks until I saw a leak on the ground.

ofcmarc

The oil swells and softens the linings and makes them grabby.


Another thing to look at is the P. Brake cables. I had a bad one that would hang a brake all the time.

sdstriper

The RWAL unit itself is suspect.

93 12v

If you live in a humid climate like I do, it's most likely surface rust. Every vehicle I've ever had has done this at least 50% of the time. Other than that, I'd suspect swollen shoes or sticky wheel cylinders, something like that.

torquefan

Wannadiesel is right. The first suspected problem is night corrosion. The drums develop a fine layer of rust from the moisture overnight, then will grab and be noisy till it's all burnt off. It's pretty common.

The second possibility is a leaky axle seal, which will allow oil to saturate the linings and change the friction characteristics, especially in changing temperatures.

ChrisLib

leaky wheel cylinder did it to mine.