it is a murray 180 tstat and the temp keeps climbing until i shut it off, then the tstat opens....its brand new.....the spring is facing down

 

Sounds defective to me. Test the radiator cap while your at the AP store getting a new therm.

 

well, its about the 3rd new one in the past 4 mo or so trying to find out my overheating probs......the cap is a fairly new 20lb one.......it did this today with the cap off, but i have an electric fan and usually when i shut the truck off, it kicks on telling me that the tstat just opened......tried to get a napa stat but they didnt have any in stock

 

IIRC, the cap is suppose to be 15 or 16 lb's only. Have you tried a Stant super stat, robet shaw, or oem thermostat ? And btw, the motor always get's hotter before it cools down when you shut the motor off.

 

If you get a defective stat, always get a different one from a different store. May be it was a bad batch. happened to me before. I'm currently troubleshooting a overheating issue as well. Maybe you have a faulty temp sensor? I'm getting ready to change mine. Only a $10 fix. worth a shot.

 

new sensors, talked to the guy at napa and told him my prob and that it was a murray and he said that alot of people have probs with them.....he ordered me a napa 180 thatll be here in the morning

i started it and let it warm up and it got up to at least 240, top hose still cold and as soon as i shut it off, the tstat opened

 

Like I said, the motor gets hotter when you shut it off, so the defective stat is finally opening at the wrong temp.