My 87 D150 truck is having a braking issue. After the truck sits for a few days, occasionally when I pull it out of the driveway the first few times I hit the brakes they are EXTREMELY touchy, usually locking up the driver side front wheel. After making a few stops, the brakes go back to "normal", but it does pull slightly to the driver side under harder braking....Any idea what this would be from? I got this truck last fall, and since them I have been fixing a LONG list of things that the previous owner rigged or fixed wrong....this probably being another.

Any help would be appreciated.

Are the front rubber lines old ?

unknown age on those, they don't "look" bad/old...but then again, I haven't had the truck very long.

Symptoms alone will get you only so far. It's time for a physical inspection.

Properly working brakes will have no:

a. Contamination on the pads and rotor, nor any source for continued contamination of same.

b. Failure of hydraulic parts (leaking or seized calipers, leaking or bulging or collapsed hoses).

c. Hung up sliding mechanisms on the caliper mountings.

If your vehicle does not have all of these characteristics, make it so.

Brake pads can be real toughy when there cold or wet. I have mostly experienced this issue when there wet and cold.
I have several vehicles that have grabby brakes when there cold or wet. And have experienced it many times over the years without any brake problems.

Last week it rained here for the first time in weeks and my brakes were real touchy for the first application.

I don't see a problem just as long as they are not locked with your foot off the brakes.