First I would like to thank speedkar9 for his informative DIY videos. I am hoping he will chime in here because this is a pickle.

I am replacing the thermostat in my sons ES330. The heat wasn't working but all the modes were so I started investigating and concluded the thermostat was bad due to the fact the hoses were feeling like they were a car tire and had no give in them which they should if the thermostat is working properly.

I know that less than 10K miles earlier, by the previous owner a service was performed which included the cooling system so it's possible they replaced the tStat at the same time. Upon removing the old one and comparing it with the new one, they are completely different so I am off to Autozone to look at some other boxes to make sure this is indeed the correct one but at this point I am thinking someone may have put the wrong one in but here is the photo and maybe you good people can add your two cents.

PS: no overheating issues because since we purchased the car our weather has been much cooler and my son only takes short trips so the car doesn't go too far. The car was in the accident in July and it sat during the hottest months of the summer, otherwise I would think the car would overheat at some point with a non working thermostat.....



New one is on the right....

 

Just wanted to add I guess it could be the original one which would make sense

 

If you get a new tstat, spend the extra money and get the failsafe one (if it fails, it fails OPEN!) and that new one COULD be the failsafe version.

 

Get an OEM replacement, no aftermarket junk.

 

They both look brand new!

 

Thanks for the tip on the failsafe units, i will have to look into that.

 

The one on the left looks like a typical OE unit. The one on the right looks like a typical Stant, etc. aftermarket cheap replacement unit.

I very much doubt the one on the left (OE) is at fault; I'd stick it in a pan on the stove and start boiling the water, see when it opens if you have a thermometer, or just how long before it boils. I'd keep it in and not use the weaker/cheaper aftermarket unit.

Heat not working usually has other causes. A thermostat stuck CLOSED would give cabin heat but cause engine temp overheat. A thermostat stuck OPEN would also give cabin heat, but only very slowly after the engine finally warmed up (you would be running two cooling radiators in the interim in effect). So no cabin heat at all after fully running up to temp would not be because of a thermostat.

Prior gen ES and GS models had notoiously bad heater valves, but I think fixed in this generation. perhaps the blower motor is not kicking in?

Basic "WTF?" checks here include making sure the prior coolant service installed/re-installed the t-stat the correct direction, did not leave an extra/old gasket in the housing, etc. I have run circles in the past on these basic issues. Never assume on diagnosing a system that the prior work was done with anything approaching real competence.