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Earlier today I drove to Walmart and everything was fine and dandy. The car warmed up to about 180* (that's more a guess but the needle was about 3/4 of the way to 200*) and maintained it. On my way home I noticed my vents were blowing fairly cold air and then I looked at my temp gauge and it was fluctuating roughly between 130*-160* (again that's guessing based on the dashboard guage). I thought it must have been a freak thing and didn't mind it too much.

A few hours later I went to the bank and did a few other things. My car warmed up to about 180* and then once again while driving it started fluctuating around 130*-160* again all of the sudden. I drove around for like 20 minutes kinda beating on the car to see if it would heat up but once I hit a stop it would just drop again.

I changed the thermostat back in September when I did my UIM and LIM gaskets. I've had absolutely no issues up until now. Did the piece of **** already break or something? That's the only thing I can think of. I can't imagine anything else that would cause this. If draining and refilling coolant properly wasn't such a pain in the ass I would just go ahead and change it out but I thought I'd ask here first.

Sounds like the Thermostat is trying to stick open..

I was afraid of that. Why couldn't this happen during the summer ?!!

Just put a tube in the radiator opening and push it all the way down. Siphon into a clean gallon jug. It'll be enough to let you swap the thermo without getting antifreeze all over.

I recently replaced a thermo acting like that. It wasn't stuck open, but the spring had gotten really weak and it was either opening early or the pressure from the water pump was pushing it open.

Some cheaper thermostats spring get weak over time. Check that the system is purged of air first and the cap is working OK with no clogs.

Have you checked the level of coolant inside the radiator? If it's low you might have an air bubble in the heater core and affecting the thermostat sensing the coolant temp. You can force the air out of the heater by having the engine fully up to temp (lower radiator warm because coolant is flowing through the radiator) and revving the motor to 2500 rpm for about 10 sec. Then repeat for a total of 5 times. With the heater blowing, you'll feel the hotter air come out when the heater core gets filled with hot coolant. Then bleed the thermostat.

If your thermostat is 4 months old I wouldn't expect it to have a weak spring or be defective yet, but it could be.
Is the thermostat in the rubber sealer ring correctly?

Is it possible the heater is drawing so much heat out of the coolant that the temp in the motor is dropping. I see you are in Minnesota. I know here it never got over 18 today and started out at 8 overnight. I would have idled it in the garage for a while to see what it did with the heater cut off and driven it some with no heater just to see.

I've had my heater cranked to the max, and my coolant temp doesn't drop. Those are the same symptoms I experienced when I had a bad T-stat. A new High quality one fixed all my Issues (mine was a Murray Ultra).

What brand of T-stat are you using?

I've had good experience with the Stant "Super-Stat." It's a few bucks more than the "regular" T-stat, but the "framework" and spring on the premium product are nice and beefy.

agrazela wrote:What brand of T-stat are you using?

I've had good experience with the Stant "Super-Stat." It's a few bucks more than the "regular" T-stat, but the "framework" and spring on the premium product are nice and beefy.

I don't know the brand but it was a 180* one that I got from Intense back when I ordered some stuff from them. I think I just got a dud . I'll go buy the super-stat when I get off of work. I'm convinced it's a weak spring or plain busted thermostat.


The puke tank is at the correct level for cold and the radiator is filled to the top as well. When I warmed my car up a couple hours ago for work (I work night shift) the car was warmer than outside so it was definitely pumping out some heat. It just seems like once I hit 180* it just stays open after that.

I know the last post was on my birthday in may but here are my thoughts anyway -

Two things to consider: 1. Check to see what temp the T-stat for your car should be; I believe most cars run 195 Degree not 180. 2. Running too cold a T-stat will result in the car burning more gas that normal. 3. (i lied, three things) -some cars have a bleeder on top of the t-stat housing for bleeding off any air traped in the cooling system.

In my experience the problem you have could be air in the system and / or a t-stat. . . . Good luck.

I've gotten some of my best MPG tanks with a 180* stat...Our cars can run either. I'm running a 180* stat to preserve the UIM/LIM for a bit longer...

Sounds like you got a bad one. Go to AutoZone and get the higher-priced AutoZone house brand 180* stat. It looks identical to the Intense stat.

Arriva wrote:I know the last post was on my birthday in may but here are my thoughts anyway -

Two things to consider: 1. Check to see what temp the T-stat for your car should be; I believe most cars run 195 Degree not 180. 2. Running too cold a T-stat will result in the car burning more gas that normal. 3. (i lied, three things) -some cars have a bleeder on top of the t-stat housing for bleeding off any air traped in the cooling system.

In my experience the problem you have could be air in the system and / or a t-stat. . . . Good luck.

A 180* Thermostat works just fine on our cars. It helps with performance, as well as MPG's.