Brakes stuck, peddle won't come back up. Cold temps.

Yes.

 

No. You will see when you get it apart. You may have to twist the plunger back and forth to get it freed up. It will pull straight up and out. Clean lubricant and reinstall including the hinge pin on the brake pedal.

 

I had KW that the plunger rusted and would stick. Sprayed with WD40 worked.
If it's freezing from water in system, take main line off, it's the stainless steel braided one and pour alcohol in line and reinstall and start truck.

 

Don’t dump air line antifreeze in the line from the compressor. The alcohol in the system after the air dryer, the alcohol breaks down the desiccant in the dryer. You might need to replace the treadle valve under the peddle, I’ve done it on both my trucks it’s not that big of a job.

 

My 1980 KW had the brake pedal stick. I tried freeing it up but it was a waste of time. Plunger was locked right up. If its the original treadle valve I'd just replace it. Cleaning/lubricating the plunger is just a patch IMO. Rubber seals harden, dry out and wear over the years.