I'm consistently at 204-207. Which browsing this thread it looks like its high....

I had my Timing job done 85K ago at Right Toyota in Scottsdale. I guess its time to take it in again but to my new mechanic. I wonder if I caused any damage to the motor having it run that much hotter over the course of 4.5 years...

Dang Tim I thought that would have fixed the increased reading in the temps.

Post pics of the two thermostats side by side.

Maybe the Aisin clutch just can't moved as much air. I compared the new Aisin one and my old one back years ago and they looked identical, even up to the spring size and fin count.

I tested the two thermostats side by side in a pot of hot water, and the old thermostat was opened 2mm more than the new one at the same temperature. After installing the old thermostat and burping the system with the Lisle funnel, my temps are back down between 188-192 for the most part. I did see 194 on a test drive afterward, but since the work I did replacing the radiator and thermostat, I haven't seen 188 in a long time while driving. So, I was running 190-196 most of the time with the newer thermostat and I'm now running 188-194 with the older thermostat. So, I dropped a couple degrees.

Was it worth doing? I guess so, and maybe I'll see even a bigger difference when the summer rolls around and I do some mountain biking trips. With the newer thermostat, I remember seeing 199 degrees going up a grade on a pretty hot day. The fact that the older thermostat opens up easier as the temperature climbs will hopefully keep my temps in the low to mid 190's all the time. I reckon I'll find out this summer.

Wow. It is pretty sad when not even the OEM parts are as good as what is put in at the factory. As the old addege goes I guess, size does matter.

I hope you enjoy the funnel; I haven't found a better way to expel air from a cooling system doing shadetree repair.

Well, my theory is this. Springs fatigue over time. It would make sense after thousands of cycles of opening and closing that the spring gets a little tired and will open farther because of it. I sort of think there was nothing wrong with the new thermostat. It just has a brand new, unbroken in spring.

I think everything would have been fine the way it was on my truck but it did bother me I was running hotter than I originally was before the parts replacements.

I wonder if they put the jiggle valve on upside down?

That's like normal. I don't understand why you guys like freak out about 190-208 temps ?

Because maybe we're slightly neurotic.

Like @jgue467 said, I bet your jiggle valve is at the 12 0'clock position. Just drain your coolant into a clean bucket, remove the lower radiator hose, remove the (3) 12mm nuts that hold the thermostat housing neck on, remove the neck and see what position your jiggle valve is at. You'll most likely see it at the 12 position so just pull it out (might take a little tug), and reinstall it with the jiggle valve at 6 position (pointing towards the ground). You will see your temps drop around 10 degrees and basically be where I was before I decided to put my old thermostat back in.

Btw, the torque spec for the (3) 12mm nuts is 14 ft-lbf.

That's what I run at also.

The engine seems to run very smoothly at that temp. I run a quality synthetic oil that can take that heat in stride.

Mine runs between 199 to 205. I will replace my tstat this summer.

No but seriously. No offense to you guys. By all means change your thermostat and the whole nine yards. I run 192-198. Hot/humid summer day with AC on. Gets up to 205 according to scangauge.

Not once did I worry. Not once did the gauge handle went up.

99% of people here have these numbers. And there's simply nothing to worry. Just my opinion.

You're probably right and guys like me are worrying about nothing. I just got used to seeing certain temps when driving and it kind of pissed me off when I was actually running hotter with a brand new radiator, brand new thermostat and brand new fan clutch. At least I was able to prove my theory that the new thermostat was the culprit for my slight rise in coolant temps. Now that I have my old thermostat in, I'll just leave it in there until it's time to renew the coolant again. But who knows, maybe I'll just leave it in there for good.

Me to. I always over analyze things on my truck.

Cooler to a point is better in my book as well.

This piques my curiosity. Next time I am in the yard for parts I'll try and find a 5vz with hopefully the originally tstat in it.