Toyota Repair: 2004 Sienna Coolant Temp Gauge, coolant temp, radiator cap

Question
I have a 04 sienna with 45k miles, i left the radiator cap off and my daughter drove it down the highway for about 100 miles, when the yellow check engine light came on, she called me and said that the other gauges were fine including the temp gauge. Then the van started to lose power and she pulled over. Thats when she noticed it overheating, but the temp gauge never went up.  The dealer said the engine is junk, only has 20 psi compression in cylinder. It needs a new engine. The service writer told me that on that year and model that the temp sensor is in the wrong spot, when the coolant is low the temp gauge will never to the hot mark.  If this is true, why should i have to buy an engine for this van.

Please can you help me out.
Thanks
Rick
989.614.6277


Answer
I don't know where the service advisor got this information but I have never heard of this and Toyota has not issued any service bulletins regarding this, it seems to me that the engine overheated because the radiator cap was not put on and most of the coolant was lost which caused the engine to overheat and self destruct, I don't know whether the temp gauge never went up and neither do I or you or the dealer, we weren't there and your daughter may not have noticed it going up.