Auto Parts: Parking brake not holding, rear brakes, disc brakes

Question
I have a 2000 Tahoe and replace the rear brakes a few months ago.  The rear on this has disc brakes but it has shoes for the parking brake.  Anyways, I replaced the shoes as well because the parking brake was not holding, and one side of the shoe was completely worn.  Now, when I go to park on a hill and put on the parking brake, it does not hold at all.  However, when I come back out to the truck to leave again, the brake is holding.  So after it sits there for awhile, it holds.  One time I was in and out of the house in just 5 minutes and when I got back it was holding.  This is totally baffling me.  Any ideas?

Answer
Hi Dan,
Actually, after reading your post, I'm about as baffled as you are. Your vehicles E-brake set-up is mechanical so when you engage the brake, it should immediately apply.
I guess the best place to start diagnosing would be from the beginning. I would examine the cable from the pedal/handle all the way back to each E-brake set-up. If there was no physical damage or alterations to the cable assemblies I would remove the disks and make certain the shoe adjusters are set-up properly. The shoes should ride on the drum at all times. You should have them adjusted to a 'slight drag'. If you are doing it with the wheel off, you'll want to adjust them to a heavy drag, heavy enough that it makes it pretty difficult for you to even turn the rotor/drum assembly that way it equates to a slight drag once the wheel is replaced.
If your problem is STILL not taken care of, I would jack and support the rear of the vehicle and have an assistant engage the E-brake while you hang-out under the vehicle and watch what is happening. From what you describe I would have to assume something should be noticeable when the assembly is engaged.
That is quite strange.
Thanks for the question, I hope this helps. Ask a follow-up if you need more info.
Knucklebusters