Chevrolet Repair: 1998 Chevrolet Blazer LT 4x4 heating, chevrolet blazer lt, 1998 chevrolet blazer

Question
I have a 1998 Chevrolet blazer LT 4x4. I recently started having problems with the heater. It was working well, however not long ago stopped blowing warm air. Cold air would come out in place. I took it to a local Bruneel Tires, and had it checked. As expected the radiator fluid was low. More digging around, and we found that the water pump was bad. So the water pump was replaced, as well as to hoses, and the thermostat. Took it home, worked great. But within 2 days I noticed that I could hear air bubble running through the lines when I would step on the gas, and that luke warm air was coming out. I returned the Bruneel, and it took some time, but they found that the intake manifold gasket was leaking. Now that has been replaced. I took it from the shop on a drive, and can still hear the air bubble, and am only getting luke warm air again unless I am riding it hard. Not quite sure what to do. Any suggestions would be greatly appreciated. Thankyou in advance.

Answer
Hi sean... somewhere in the cooling system it is still sucking air... also check the cooling fan, is it running all the time. clutch should only run the fan once the truck reaches temp. check temp  at the block and then the heater hoses they should be close to the same after theromstat opens up. check and make sure that it is a 195 degree thermostat...not a colder one, i have seen 165 s put in by mistake. or that it is not stuck open.... hope this helps...merry christmas