my Toyota sienna is registering that its hot but using a laser thermostat shows that its not running hot , water pump has been changed along with a thermostat and new Asian coolant , also when the heater is turned on it blows cold so i am wondering if it could be a clogged heater core

  • The engine does not rely on the heater core for cooling - as it can be turned off. A classic "trick" to reduce overheating was to put the heater on hot to help the radiator. So, check the radiator and perhaps "flush" the system. Not sure what "asian" coolant is... Is it a recommended Toyota coolant? Do check other posts on here as they all cover points you should consider.
    – Solar Mike
    Mar 5, 2021 at 6:50
  • 1
    What did you point the laser thermostat at?
    – HandyHowie
    Mar 5, 2021 at 12:21
  • I think OP meant "Aisin" coolant.
    – EᑎOT
    Mar 5, 2021 at 16:36

1 Answer 1


If you are sure the engine is not warming up, yet it shows as hot I'd suggest replacing the coolant temperature sensor.

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