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Temperature Gauge reading low.

03Explo20

Well-Known Member
Joined
January 4, 2013
Messages
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City, State
Jonestown, Pa.
Year, Model & Trim Level
2003 Explorer XLT
I changed out the entire t-stat housing over the summer which came with a t-stat installed. Everything was working okay until the cold weather hit. Now the temperature gauge will only go up one line and the heater blows mildly warm air. The gauge does go up to where it normally did before the housing change but only after driving hard for a while.

Could this be a sign of a stuck open t-stat? All fluid levels are good in the bottle. I'm hoping it isn't water pump or heater core related. I have no smell in the cabin or any frosty windows so I'm kind of leaning away from the heater core. Could the t-stat that is in the truck possibly be a higher temp stat?

I have a factory Motorcraft t-stat that I'm going to put in but am trying to think ahead in case that doesn't do the trick.
 



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Could this be a sign of a stuck open t-stat?
Could be. I had a brand new thermostat that never opened. Complete new engine that didn't get 2 miles before I had to put the old thermostat back in.:(
 






I changed out the entire t-stat housing over the summer which came with a t-stat installed. Everything was working okay until the cold weather hit. Now the temperature gauge will only go up one line and the heater blows mildly warm air. The gauge does go up to where it normally did before the housing change but only after driving hard for a while.

Could this be a sign of a stuck open t-stat? All fluid levels are good in the bottle. I'm hoping it isn't water pump or heater core related. I have no smell in the cabin or any frosty windows so I'm kind of leaning away from the heater core. Could the t-stat that is in the truck possibly be a higher temp stat?

I have a factory Motorcraft t-stat that I'm going to put in but am trying to think ahead in case that doesn't do the trick.
@03Explo20
Stuck open, or stuck partially open. Even with NO thermostat, the engine should get just about normally hot, given normal ambient temps., not -30 degrees. imp
 






I'd concur, first notch is 135°. If it's cold out and it's stuck open, you may get that temp on long drives. But it shouldn't run that cold with a stuck open tstat regularly. Put a piece of card board in front of the radiator (condenser) and drive for a bit. See if temps go up.

Also, run with an OBD2 scanner and see if that's actually the temps the PCM is seeing.
 






Changed out the t-stat with a Motorcraft stat and all seems okay once again. The cheapy that was in the housing unit looked like it was in the open position.
 






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