Hi. I just finished installing a new water pump and t'stat in my 06 M/C. It all started with cold air at idle and correct warm air at driving. Started with a anifreeze leak right near the water pump. Never over heated. I believe the leak is stopped, I still have the cold and hot problem. I put new Dex Cool in, Ran until the t'stat opened, opened the rad. cap and I could hear the system burping thu the reservoir tank.
Added more Dex Cool. I still think It needs be bleed. Can any one guide me thu bleeding this or send me to a site that has this info. I had to do this outside and was afraid to flush the system. The Monte only has 35,000 miles on it.

 

Is there a bleeder screw around t-stat housing? I'm not sure how your 3900 is, but with a 3800 you bleed out the air through the screw. It might take 10-15 minutes to bleed the system.

 

No bleeder on the 3900. Only on the V8.

 

Anyone out there?????