Sorry about the hijacking... Starting new thread.

Hey TMS, yes, bled the system this weekend. I know the vacuum is for mode and not blend, but makes little sense to me that replacing the check valve seems to have made things better when previous revving did nothing. It could all be a big coincidence and my flushing the core and bleeding are completely unrelated to the check valve. But I've got better heat now with the blower on High than I did before. I'll have to check the blend door operation next weekend.

 

you need to double check your coolant level. I thought mine was full, but added over a gallon of fluid! Take the cap off and start the truck..with heater on hot and blower on high top off the rad. and rev the engine a few times... keep doing this for like 10 minutes. Fill up the over flow res as well

 

Did that for over an hour on Sunday. Added about 1/2 gal in that time. Though, I only revved a few times, I did let the engine run for close to 1.5 hours while testing the heater.

 

Did you have it on a nose-up incline?

 

This is a classic case of the heater core being partially clogged. You can check the blend door by rapidly turning it from hot to cold, put it in the center and quickly move it to hot,then put it back in the center and do the same to the cold side, you should hear it slam shut it either direction. And you can also adjust the cable with this procedure,