Engine temperature drop

[2007CorollaCEOwner]

Hi,

Today when I started driving my 2007 Corolla, I put heat direction to windshield. After driving 15 or so minutes the engine reached it normal operating temperature (gauge raised to the middle of the scale).
Then I stopped and with engine idling I started swicthing heat flow direction to all other positions. The engine temperature started dropping.
It dropped about two notches from the middle of the scale. It statyed there for a few minutes and then returned to the normal operating temperature.

I am wondering what could be the cause of that ?
I scanned the trouble codes after that. There were none. Neither P0125 nor P0128.

Thank you,

[Tech1984]

Hi, and I take it you are introducing yourself and you also have a issue with your Corolla.

You are in the perfectly normal range of engine temperature. If you were to have a problem with engine temp range performance, it would have a code p0125. Just be sure your coolant bottle is between low and full.

Drive it, and quit worrying.

[TrailDust]

Originally Posted by 2007CorollaCEOwner

Hi,

Today when I started driving my 2007 Corolla, I put heat direction to windshield. After driving 15 or so minutes the engine reached it normal operating temperature (gauge raised to the middle of the scale).
Then I stopped and with engine idling I started swicthing heat flow direction to all other positions. The engine temperature started dropping.
It dropped about two notches from the middle of the scale. It statyed there for a few minutes and then returned to the normal operating temperature.

I am wondering what could be the cause of that ?
I scanned the trouble codes after that. There were none. Neither P0125 nor P0128.

Thank you,

Like eyeball said, it's operating within the proper temperature range, which can be slightly variable due to conditions. Don't forget that--in essence--the heater unit in your Corolla is just another radiator, and when all heat is selected that's a lot of heat being removed from your cooling system as a whole, and the engine compensates by restricting the thermostat to help increase temperature at the engine block. Small engines will see changes like this much more often than some huge V8. Again, it's normal.

[eyeball96]

Like Traildust and Tech1984 says...its normal. Just drive it and enjoy

to ToyotaNation

[2007CorollaCEOwner]

Thanks to both Tech1984 and Traildust for the explanation of this behaviour, which I never observed on other cars. I simply experienced in the past on other cars the thermostat stuck open and that is why started worrying. Those cars reached normal operating temperatures when outside temperature was not too cold but failed to do so when it was -20. So, I simply wanted to know if it was a sign of a thermostat starting failing. Thanks again.