Cooling problem

[kimncath]

First time here, lookin for some help guys. I have a 97 olds silhouette and it decided to overheat, guage went up, stopped for awhile and it went down. Had my garage change the thermostat and it has done it again. Now I have a new waterpump and it is still registering hot, back and forth, blowing cold air(it's freezing outside) and my low coolent light now strobs on and off sparatically. Antifreeze is good! Any suggestions on where to look now?? It can run for awhile and dance back and forth between cool and hot, its just the Hot that bothers me. I don't want to ruin the engine. Thanks in advance. I love my van and never had problems with it till now. Bought it used.

[Milo2001]

With all the new parts, I would want to check out the temperature sending unit. You want to verify that you actually have a problem. Also it would not be the first time a thermostat was bad, even a brand new one. As far as the the no heat goes, verify the hot/cold damper is working correctly. How's the condition of your radiator? Any blockage, you need a new one. These new cars were built with the smallest aluminum radiator they could fit without the added weight. They were at the max for cooling brand new, so any blockage its operating at less than efficiency.

These systems also need to be burp. Make sure your garage bled all the air out of the system. If you get a pocket of steam that hits the temp sending unit, the gage will spike.

Good Luck

[94 Jimmy]

Yup, you need to bleed the system, any air will collect in the engine and cause an air lock. The thermosensor will read the temperature of the air instead of the coolent and will bounce around.
To bleed the system find the two small brass screws, one on the thermostat housing and one on the riser near the water pump. With the engine running or pressurized open each screw carefully about a turn, (watch out it's hot) and wait until a steady stream of collent comes out, this will evacuate any air.
Where does the air come from you ask. Well when the parts were replaced perhaps your mechanic didn't bleed the air out of the system when he refilled it. That's the good news.
The bad news is that a leaking head gasket could be allowing exhaust gas from the combustion chamber into the water jacket. Does your oil have any white goo in it(looks like dirty mayo), if so, stop driving immediately because the contaminated oil is not protecting your engine and you may destroy it. Is there any foam or bubbles in your coolent recovery tank, if so this is probably exhaust gas getting into the cooling system.
Read my reply to risingernicole in his post titled "Head Gasket" for my leak stop procedure. Its worked for me on a couple occasions and is worth a try.
Good luck
Let us know what you find.
94