I tried the TRD 70 degree thermostat and didn't notice much of a differance in the operating temperature. After putting in the Mishimoto 60 degree thermostat the idle smoothed out and the car is running much cooler. It threw a code for low thermostat operating temperature twice but seams to have adjusted. I haven't had a check engine light now for 2 weeks of city driving, no misfires, no O2 sensor voltage, no low thermostat operating temperature.

 

I've always been courious.... why change out the thermostat? what are the benifits?

 

really not necessary if not no point at all if you are not modified.. well i take that back partially, maybe on really hot regions it would help maintain lower coolant temp. But always keep it within normal operating temperature, running on temp too low will not be so good.. the car's in calibrated to perform well within its defined operating temp, too low might cause oil not to flow very well or more unburnt fuel due to too low core temperature.. even the engine internals might not be on its desired tolerances and cause more wear on the motor.

Rule keep it low but on operating temp.. im gonna say around 171-181F is a good spot

 

from what I have read, if u keep the temps too low there is faster engine wear. I remember seeing a graph comparing from 150-160-170-180 and so on and 180 to like 260 the wear was pretty close to nothing. Then from 170 and below the wear would multiply by as much as 3% every 10 degrees. Hence another reason to take it easy when starting the car cold. If I remember correctly it was in a Ford car, but still it's the same principle. On top of that I saw something about unburnt fuel crusting up around the valves. I think it was at much colder temps that ur running, but hey, something to think about.

I stay in the mid 170's just cuz I'm turbo'ed, if ur stock and don't live in a really hot region I don't see the point.

 

Cooler temperatures aid in controlling detonation, but modern engines are designed to run pretty hot. The heat aids in complete burning of the fuel for emissions purposes.

 

the mishi one is at 140 F

Do u guys think thats too low???

 

If you're not boosted and don't need the added cooling, I'd say its too low. I'm sure the engineers at Toyota thought about this more then we have...

 

140 is too low.. might even get bad mileage running that temp.

 

Just because the thermostat opens at 140F doesn't mean that the ECT will be maintained at 140F. When I had the stock 180F thermostat my ECT got as hot as ~220F. With a 170F stat my ECT still reaches 200F on cold days and 210F on hot days. EGT is a more reliable indicator of combustion chamber temps than ECT. You can see both with an OBD2 scan tool. I've seen EGTs as high as 1700F with and without the turbo. That's more than hot enough.

Considering that Madmarx lives in AZ, the 140F Mishimoto is probably a good choice. I could probably benefit from a 160F stat here in MD.

 

Thats true, doesnt mean your 140 thermostat will keep your coolant temps at 140 all the time.. I have a 170deg thermostat and its keeps my temp 170-190F, im gonna says it is well matched with my setup. On really hot days and prolonged traffic i can reach 200-210F

oh i didnt know stock is 180F, ive always thought stock opens at 196F and shuts off at around 180s.

 

I was surprised to see a 180F oem stat. I expected a 195F too.

 

Glad to hear the Mishimoto Thermostat worked out for you. I have been thinking about installing one when it hotter out around here.

 

Like a fool I installed the Mishimoto t-stat last summer. I knew it was too cold but did it anyway. Since then, I get a near-constant P0128 for t-stat performance. It might be okay for those in very hot climates but even MD is not hot enough. The CEL threshold is 150F and if the ECT remains below that for long, the CEL will appear, again and again.

My advice is to leave the oem 180 t-stat for IHE and go with a 170 or 160 t-stat for boosted engines. Possibly the Mishimoto 140 for very hot places like AZ. I'll be re-instaling the Stant 170 t-stat ASAP. I'd go with the TRD 160 but it doesn't seem worth the money for another 10 degrees.

 

trd tstat is about the coldest you want to go, our stock radiators have no issues keeping the car cold even on turbo applications. I went the TRD one and it still runs a little on the cold side, 140 imo is way too cold if thats what its running at. I agree 100% with fred, for the turbo app go the trd tstat. At my cost its not too bad hehe.

 

Yeah, the 140F Mishimoto is fine for the summer but too cold for MD winters. IIRC last summer my highway cruising ECT was around 160F with the Mishimoto vs 180F with the 170 Stant and 190F with the 180 oem stat. The Mishi runs about 150F in winter. ECT is ultimately limited by the cooling fans in traffic or idling and I've seen it peak at 215F on a 100F day with any t-stat. Then the fans bring it down to 200F until it climbs again and so on.

IMO 160F is ideal but I refuse to pay ~$90 for a $20 t-stat! I'd rather live with the 170 stat.

 

Good news! I found a 160F thermostat that's not TRD and doesn't cost $100. It's made by Motorad and I got it shipped for only $23. That's all a t-stat should ever cost.

https://www.carpartsdiscount.com/aut...tml?3593=95910


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I've been looking for an alternative to the TRD unit!

Have you experienced any issues with the Motorad?