2006 XC70 Heat's up then cools down at stop lights

[IVIUSTANG]

Hi Guys,

Last winter I had the fun of slow coolant heatup, so I replaced the thermostat and coolant. Also in the summer I did a complete timing belt job including water pump.

However I am still having the same symptoms as last year, at -15C or colder the car warms up really slow, and once it finally is up to operating temperature; at stop lights or when idling the temperature gauge will actually dip down a few lines. When it is -25C like tonight the temperature gauge goes to around 1/4(when halfway is normal) when my car is idling. I can't handle this, it will get to -40C and I need this car to be a heating machine!!!

My previous Volvo(1998 S70 T5) heated up MUCH faster than my XC70 and it didn't have the temperature drop.

Anyone have any ideas other than thermostat or coolant?

Thanks,
Jesse

[quahog pearl]

Try taking the thermostat out again, and here's why: I think it's possible to put thermostat gasket on one side of thermostat ( instead of around it with the major OD of thermostat fitting in the gasket slit) and you can get enough leakage to partially circulate into the radiator. It's an easy thing to miss

[IVIUSTANG]

The gasket is seated correctly, I made sure of this when I installed it. Anything else?

Thanks,
Jesse

[oragex]

With the engine cold, start it up and let it run for a few minutes. Put your hand on the top radiator hose, where it gets into the radiator. Is it dead cold? If it's a little warm, the thermostat is stuck open.

You can also disconnect the hose at the thermostat with cold engine and check visually the top of the thermostat.

Also, check for radiator fan not turning off.