you could do that as well, but thats one i havent heard of yet nor tried. give the above a shot if that doesnt work then you may actually have a t-stat sticking. doesnt really seem like it totally yet other than you mentiond it started when it got cold. thats when alot of thermostat issues show up. like mine

 

got it.

the pail with lil hose to the bleeder worked. I did have to jack the front up.

It took maybe 45 minutes to make sure all the air bubbles were out but now my heat is scorching hot!.


basiclly get the snap on company"s coolant funnel. attach it to the rad.
run a rubber hose to bleeder valve on intake manifold.
open plug by fire wall and manifold plug
put the opposite side of the hose in the funnel. fill the car with coolant
when it starts comming out the bleed pipe and valve cap them both off.
start the car with heater on high. let the car get pressurized and watch the bubbles in the funnel come up. once they stop every say 10 minutes open the bleeder valve with the opp end in the funnel. I found this showed you the air comming out and when the thermostat closed it sucked more coolant in replacing the air. the last time i let it build pressure for 15 minutes went to bleed it and not bubbles.

 

Snap on also sells a tool that sucks your cooling system into a vacuum and then you let the vacuum pull the coolant it. Works wonders i use it at work all the time

 

yea saw that too, if I had trouble last time I was going to buy it today when the truck came by