Thermostat stuck open?

He's probably right. I was monitoring coolant temp with ScanGuage, and the temp range you mention is similar. The only time I recall seeing it shoot right up to say 190F was climbing a local ski hill.

One way to test, except you need to extract it: suspend it in a pot of water on the stove, with a thermometer in the water as well, and watch it's performance as the temp rises.

If you've still got the old one, suspend the two of them side-by-side, watch for differences.

 

When the engine is hot, Carefully, touch the upper radiator hose. and bottom hose.
They should be hot. And since you are getting heat in the cabin, it's likely working correctly.

Those temps are fine. Because the NEW coolant pump is functioning correctly.

 

EGR ever cleaned?

 

Do you have the latest SW update?
I had it done for free.
The TSB mentions 'Water Pump duty cycle changes' and the European version of the TSB mentions 'Head Gasket life'.
Sorry I don't have the numbers, but you can find them, or just call your dealer and 'demand' you need that TSB performed.

It would be interesting to see if your temps are different with the latest and greatest SW in the ECM.

 

I'd recommend every 50k miles max.

 

Mendel Leisk said: ↑
EGR ever cleaned?

That is just a picture of the 90° pipe from the EGR Valve to the Intake Manifold.
The problem is the clogging that happens in the tiny passages in the plastic manifold.
There is no way to 'check'. He only expressed his opinion.

The manifold has to come off to 'check' and while it's off it should be cleaned. Cleaning the EGR cooler is a bigger job, but if it is clogged a bit, that is not the big problem. The intake port clogging is the problem because they clog unevenly.

I haven't cleaned my EGR system yet at 155k miles. But I imagine small rotary wire brushes run through the tiny ports should do the trick.
A bigger brush for the big horizontal EGR port,,, and Bob's your uncle ! Maybe a quick spritz of cleaner and the intake is ready to reinstall,,, IMHO.
What's he going on about "another week"???

My temporary fix is Disconnecting the EGR valve. No problem found in 2000 miles. Many here are doing it.

 

The colloquial namesake “cooler” (Toyota just calls it “pipe”) is due to the radiator within that component. “Clogged a bit” may continue to allow so-so flow, but cooling is also reduced. By how much a mechanical engineer will maybe weigh in.

 

That should be an easy test.
Use an IR temp reader on the gozin pipe and the gozout pipe from the EGR cooler. Before and after a big cleaning.
A quick stop while on the highway, pop the hood, take the reading.

More accurate would be to have a person hang on in the engine area with the hood open at highway speeds.
Or stick on thermocouples on both pipes and a display for those two sensors.
Place yo'bets. How much temp drop going through this cooler?

 

I have monitored my engine temp for years and it reaches 190f even in freezing weather. I also have the revised egr valve, intake and ecm software.

However it won’t code for low coolant temp until it can not reach 167f. So you won’t get that code, at least not until it is cooler out.

The thermostat begins opening between 176-183f and is not all the way open until 203f. So it would seem the main engine coolant flow through the radiator is shutoff.

The heater, egr and throttle body flow bypasses the radiator and thermostat valve so heater operation is not a good indicator of thermostat function.

Finally large thermal swings are not good for the engine.

 

I've installed a block heater a few days ago, after 2 hours the coolant increases 30° compared to ambient temperature, but as soon as the engine and the coolant pump start, the temp drops about 10°.

Is this expected and caused by the mentioned egr throttle body and heater bypassing the thermostat valve? Or is my valve stuck open?

 

This is due to the fact that the liquid from the spot heater does not circulate throughout the entire circuit, which remains cold in the main mass. When the engine is turned on, the hot liquid begins to circulate, mixes with the cold areas, where it cools down and the temperature levels out to a decrease on average.

 

Just editorial: that's centigrade degrees I'd assume? (mirrors my experience)

 

As before your experience in that ambient seems normal.

I doubt your thermostat is stuck open. In addition to the egr, throttle body and heater bypass there is the exhaust heat recirculating system initially adding ambient temperature coolant.

However if you want to verify when the thermostat opens, you can watch for flow in the coolant reservoir. It may require a strong focused light to see through the plastic.

...................
You can place the engine in a continuous running "maintenance/inspection" mode to observe coolant flow:

Toyota recommends having the AC-compressor off and do not routinely drive in this mode.

 

correct, it's centigrade degrees

 

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Why our thermostat opens at 82C instead of 88C?

There is a 88C version for the G2, according to Ken1784, and he acieved better fuel
economy.

Stuff you can do to improve your winter mileage | PriusChat

Is there 88C thermostat version for G3?