So I was flushing my radiator today in preparation for a water pump change and I decided to take some temp gun readings. The thermostat housing read about 220 to 230 degrees on the gun while inside it was not even at 210. Electric fan was not running yet. From measuring things inside the house, it seems that the gun can not be off by that much (not 30 or 40 degrees certainly). Does this make sense to anyone? Could it be that the housing is just hotter than the coolant that is running through it. I'm getting about a 20 degree drop across the radiator (measured at lower and upper radiator hoses). I would imagine that if the temperature were really 220 or 230 then the engine would really start to shudder and kick, like it has before when I got it there

 

Factory temp gauge may be wacked. We've momentarily seen 230 display on the ScanGauge and our infrared temp gun will be <5 degrees different than the ScanGauge. Motor should run like a top even at 230.......never seen the idiot light even flicker at 230. Wouldn't think the housing/cover would be any hotter than the coolant.....maybe a tad less.

FSM says fan on temp is 218.......when our fan turns on, ScanGauge displays 217-220.

 

Okay interesting. Normally when I watch my fan it turns on at 210 (on the gauge) but it does not surprise me that number is inaccurate. I've noticed that the gauge goes from 100 to 210 and then 260. It seems to me that the middle should be 180, considering it's halfway. I guess this is a good argument for some aftermarket gauges though. Thanks for the information!