Pontiac Repair: 98 pontiac transport, air pockets, pontiac transport

Question
I developed a problem when the cars temp gauge went up and the engine was sluggish and then the temp went down and operated normal then it went up again and the same thing happened. I replaced the water pump and thermostat and still have the same problems. The air coming from the vents will fluctuate from cool to warm also

Answer
Hi
The gage goes up and down? Do you see any coolant leaking?
I would have the cooant system checked for leaks internal and externally.
I would make sure there are no air pockets in the system.
Air pockets will create problems like you explain.
Please follow post back, if needed.
Pawl