For the past month i noticed my 3.8 has been over heating randomly. Sometimes it'll start to over heat after 10 miles and sometimes it won't overheat until a few days. I replaced the water pump, both heater hoses, radiator cap. I can't find any leaks but i do have to put more antifreeze in it every so often. I was told might be head gasket going bad but it doesn't run poorly, no white smoke from exhaust. What other symptoms should i check for? And what's weird is everytime i make a left turn the temp gauge drops down to half way mark or below. And the temp gauge never stays on hot, it fluctuates.

I don't know anything about this problem. What should i check for or replace? Anyone have a similar problem?

 

I would be leaning towards a sticking thermostat, maybe something to check.

 

A sticking thermostat would make the engine overheat, but that wouldn't explain the disappearing coolant, unless you're boiling over when the engine overheats.
How much is "more antifreeze", and how often is "every so often"?
If you have no external coolant leak, then either somebody is sneaking into your engine compartment and stealing the coolant out, or you have an internal leak (bad gasket).

 

I bought a new thermostat. I'll change that next. I don't add a whole lot, I never really measured. I do it every few days just to keep it from over heating as fast. Its not like it goes empty. I never tried running it without adding any to see if it does goes dry in fear of ruining the engine or something. But would a sticking thermostat make the gauge fluctuate?

 

And also if i did have a bad gasket wouldn't that make the car run poorly, white smoke from exhaust and milky oil? I don't see any oil in my coolant either.

 

My car had no symptoms other than adding coolant. It even passed the test where they check for gasses in the cooling system and it held pressure overnight. I only let mine run hot one time and in the shop it went. They couldn't find anything abnormal really with it until they tore in the engine. My gaskets were great but the head bolt was broke and oil and coolant were mixing in the intake valley. It ran great though. No smoke and it ran smooth. I was just losing coolant.

 

Turns out it was the right heater hose that goes to the heater core/firewall. I didn't have it clamped tight enough. Durr! My screw up.

 

Glad you found it.
Easy fix.