I have a 06 rwd gs300, the car seems to take awhile to warm up. I can drive about 5 miles in the morning and it will be barely halfway to normal temp on the guage. Also the heater doesn't get real hot even when set to 76 degrees, kinda suspect the thermostat is stuck open. I topped off the coolant in the expansion tank and checked the coolant cap on top of the engine. Anyone else had a similar experience? I'm outta warranty (52,200 miles) and will diy it if I decide to change it. Seems the thermostat is part of the housing but it looks easy to get to.

Thanks for any info.
Keith

 

Yes. stuck thermostat

 

I am experiencing the same thing you are, but only when the temp outside is in the low 20's or lower. This has been happening since day-one when I purchased the GS over 4 yrs ago. I chaulk it up to being normal. Now when my GS gets to full operating temp, I have to turn the heat down for it gets nice and toasty inside.

 

There are a few simple ways to check if it is stuck open. The upper and lower radiator hoses should both be about the same temperature when running. On most cars you can tell when the thermostat opens because the upper radiator hose will be cold until it opens and then warm up instantly when it opens. You can also usually feel when it kicks open because you can feel the increased pressure.

Typically Toyota's have a very specific way to bleed air out of the system, which is typically another cause of what you are experiencing. Low fluid can cause this as well.

 

Thanks for the advice, it my be some air trapped as you said. I'll have to feel the radiator hoses and see what I find.
Thanks,
Keith