Thermostat opening temperature

[rcy]

I noticed my vehicle (2006 RX400h) seemed to take a long time to warm up during a recent cold spell (-15 celsius). I hooked up my Scanguage II and found it to be 180 F on the highway.

The specs for the thermostat per the shop manual are

"Opening Temperature C (F) 77 - 82 (171 - 180).

Based on this, do you think my thermostat is operating properly, or maybe stuck open a smidgen?

Thanks.

 

[ARCOgraphite]

Dont worry, its hybrid warmup blues. Do not expect a thermostat issue. Let Lexus know, there may be a soft fix. -15c is not that cold, that +5 f. Ok Its a bit chilly.

 

[rcy]

I understand a hybrid might take longer to warm up because it's not always running. The thing is, when the outside temp is that cold, the ICE runs continuously after starting the vehicle and I'm on the highway within 3 minutes and the ICE runs all the time (mostly) at highway speeds.

Are you saying that, even with the engine running all the time, there is something about hybrids (too efficient??) that causes a long warm up time?

Thanks

 

[bepperb]

That would be perfect for being open.

The info you give doesn't really tell if it's closing all the way. If you let it idle for five minutes after the highway, does it stay around 180?

 

[rcy]

Oh, yeah, sorry. Once it hits 180 it pretty much stays there. Idling, if I remember correctly, stays around 180 or even creeps up till the cooling fans kick in. Might drop to 177 or so if I crank the heat up to full.

 

[cchase]

Stuck open will drop the temp significantly. Steady temp = good thermostat (or a weird coincidence of ambient temperature and engine load).

 

[mechtech2]

Thermostat ratings are the OPENING temperatures, not the running temperature. This is when the valve STARTS to open.

So your thermostat is not stuck open , but possible the opposite of what you think- it is the at the high end , not the low end of it's rating.

With small engines and a lot of aluminum, it is tough to retain heat in the engine on cold days on the highway. The radiator is cooling the coolant real fast with the very cold and fast airflow/exchange. The thermostat is treading water at this time - just staying alive.

Anyway, your readings seem very normal.

 

[rcy]

Thanks.