Mechanics

WHY IS MY ENGINE OVERHEATING?

1996 Chevrolet Lumina • 163,000 miles

I have a temp guage on my dash and for the last 5 months, my engine overheats sometimes, more lately, and when it does it:
1. Blows only cold air into the car
2. There is no steaming from under the hood
3. When I stop or slow down, the temp goes down.
Many times it will all of a sudden stop overheating, and the temp gauge's needle drops very fast to normal operating temp and then it will blow warm air into the car again, and will not overheat for the rest of that trip.
It's been overheating more lately.
Five months ago when this started I took it to a mechanic. They checked for leaks and fluid levels. They were fine. I had them put in a new thermostat. It continues.
I had the radiator flushed and the overheating continues.
I can't think of what it could be because it doesn't always overheat and sometimes it quits and just like that the temp drops.
Got any ideas?
My mechanic wants me to bring it in when it is overheating so they can check the temp to see if it is actually overheating - maybe the temp guage isn't working. I still have to ask - well why does it blow cold air into the car when it is doing that.
I read about catalytic converters, but I still have to ask, why sometimes yes and sometimes no?
So, maybe the water pump? Can that not work and then all of a sudden work?
Yesterday my driver's window wouldn't go up (elec). But that can't have anything to do with overheating.
Any ideas?
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320blake
February 20, 2012.



Recheck the thermostat, have the cooling system bleed, if it continues have it block and pressure tested-

Rasmataz
Feb 20, 2012.