I have a 2002 dodge stratus 2.7l. car seems to have bubbles in coolant straight water it dont do it right away takes min or 2 they start slow and get faster as it warms up.. I have ran it down the road, let it sit in the yard running with no over heating.. is it just cause im running straight water or could it have something to do with thremostat or something? thanks

 

You can try openning the bleeder screw and see if any air comes out of the cooling system. Is the car overheating? I would use 50/50 coolant/water.