Thermostat going up and down

[wagslick]

We have a 2003 Malibu v6. My wife pulled over and called because the overheating light came on and the temp gauge was pegged all the way. She started the car a few min later and everything was fine again. I drove it just the other day and watched the temperature go from no temperature (gauge all the way to the bottom) to hot (all the way to overheating) in under a minute. I kept driving and the temp went to normal then back to hot again all within about 2 minutes. Is this a cooling issue or a thermostat issue? My father in law says replace the thermostat and it'll be good. Any ideas?

[DeltaP]

Possible air in the system due to a very low coolant level.

[gmtech1]

As stated above, check your coolant level. You may have a coolant leak. Were the cooling fans running? You say the gauge was pegged hot? It's also possible you have a bad temp sensor. Yes, a thermostat is also possible.

[DeltaP]

I agree.

[j cAT]

Originally Posted by wagslick

We have a 2003 Malibu v6. My wife pulled over and called because the overheating light came on and the temp gauge was pegged all the way. She started the car a few min later and everything was fine again. I drove it just the other day and watched the temperature go from no temperature (gauge all the way to the bottom) to hot (all the way to overheating) in under a minute. I kept driving and the temp went to normal then back to hot again all within about 2 minutes. Is this a cooling issue or a thermostat issue? My father in law says replace the thermostat and it'll be good. Any ideas?

since this is always failing look for this . when in the overtemp range is the engine really overheated ? are the fans running ?

coolant should be a pink color . if its dark brown you may have sludge in the coolant from mixing dexcool with non gm approved dexcool spec.

when this occurs blockages cause this type of issue ....

[Tech II]

Like the guys said, check the level first....

[wagslick]

Had coolant flushed and filled. The temp gauge acted normal for a while.

[j cAT]

Originally Posted by wagslick

Had coolant flushed and filled. The temp gauge acted normal for a while.

did you have the sludge in the coolant/engine ? if so keep close watch on the coolant to get sludged up again. only use distilled water and dexcool ..try to keep it at 60 % dexcool to 40 % distilled water. you can go up to 70% dexcool for max protection .