intermitent cab heat,

[duddy]

Starting to get a little pissed off at my truck. I left on a trip for work dec 26, parked my truck at the airport. Came hone Jan 18, since then I have gotten what seems to be an air pocket in my cooling system. I have tried a few things with no luck.

The Issue, as the engine warms up, I have cab heat, until around 150 degrees. Then the issue starts it goes up another 10 degrees while the hvac does not push any warm air, just cold. and does this off and on until it hits 205 degrees and then settles out to 190 to 195.

I knew the coolant needed to be changed, so i flushed the system, and refilled with cat elc, changed the coolant and put a vacuum on it for a few minutes after it was full to try and pull the air out.

There was no work done to the truck, that could remotely affect the cooling system, that was done prior to the issue. I picked up t-stats today to throw in since I am sure they are starting to get weak. Not really in the know on how the system purges, so any insight would be helpful.

 

[suprdzlduty]

Wouldn't think you could get a air pocket in the system without draining the system, sitting still etc...there have been issues with the blend doors in the cab. Most of the time you'll here them clicking when the key is on, not running. Don't know if that would cause total loss of heat though. Usually loss of heat in the cab indicates a weak headgasket.

 

[duddy]

The only thing that lead me away from the hvac itself was the relation to coolant temp. It is completely predictable, down to a degree or 2. That is why I was thinking tstats sticking. But I have not been able to come up with reasonable reason to prove it to myself. I have a set that is going to be put in this weekend if I can not find anything, to cold outside to have no heat.