P0128

how do i test if the sensor is working?

 

yes please have a reading i almost drove to autozone lol

 

That is correct. Thermostats are designed to fail in the open position to prevent overheating. But yes, it will never reach normal operating temperature because coolant is constantly flowing rather than just at the 180°F it was designed to open at. OP also stated he drove for a while and got the readings in the photos.

 

It's probably just as much of a pain to replace as it is to test. You may as well just try replacing it. Worst case scenario, you have a new coolant temperature sensor and it wasn't your issue. You could probably return it too, but that would involve taking it back off the engine.

 

I finally located my thermostat its in a open area thank god lol. I saw some videos and some are like under the alternator lol.

 

for sure I'm going to purchase both just to eliminate any issues good thing they are not pricey at all. Thanks for the advice guys!!!!!

 

It's a mechanical system. It isn't full open or full closed and that's that. The valve opens only when the temp is hot enough. The hotter it gets, the more it has to open to maintain the amount of flow necessary to keep the engine at the right temperature.

It's basically a valve held shut by a spring (simple explanation anyway). Once the coolant gets hot enough, the valve overcomes the spring tension and the valve begins to open. If the spring fails or a seal fails, coolant will constantly be flowing and thus the vehicle will take longer to get up to temperature, or, most likely, never reach full operating temperature.

 

another question is it best to make the 50/50 coolant myself? or should i get a prediluted one?

 

It doesn’t really matter - just do whatever’s cheapest and easiest. Just use distilled water if you’re going mix your own. Testing your thermostat in some hot water on the stove with a thermometer would be a good idea before blindly putting a new one in.

 

Eh shoot. I might had been thinking the 3.4. Sorry.

 

yes i will test it out! i saw a video on that!

 

And yet, that's not how it works. The thermostat only opens at a certain temperature. So yes, it can, technically, open and shut repeatedly. However, your engine makes far more heat than 180°F, thus the need for a cooling system in the first place. Again, it isn't necessarily operating at full blast once it does open (it doesn't just shoot to full open when it opens). But again, they're designed to fail in the open position. Thus why the OP's temperature reading, also shown by the gauge (2 different types of readings) show the temperature far below the normal operating temperature.

 

There's a lot of stuff you're missing here. A thermostat is NOT the only part of a cooling system that can fail. If for some reason the thermostat fails to open, your car will overheat. If your water pump fails to pump, your car will overheat. If you're running the engine at low speeds in hot weather with no electric fan or air speed, the engine will overheat.

Now: addressing your 136° comment. A thermostat doesn't run that low because it is too low of a temperature for the engine to run at. "Operating temperature" is the temperature in which the motor runs optimally and incurrs less wear. You may notice that the temp gauge has a wide range for "normal" which is because there is a threshold as well.

What you're trying to explain is that the coolant that is in the radiator, and thus not in the engine, is cooler. But there aren't 2 valves, there's one. Coolant may not be flowing to the radiator due to the thermostat, but that doesn't mean it is completely blocked off. It isn't like there's just nothing past the thermostat. That would be an air pocket and those generally aren't good or efficient.

The engine is constantly producing heat. The coolant takes that heat away and radiates it off through the radiator. The cooled coolant then flows into the engine to then take the heat away and the cycle continues.

The thermostat is not suddenly fully open once it meets 180 degrees. It is a simple mechanical system that has been used for decades because of its simplicity and it works well. It controls the rate of flow of the coolant relative to the temperature of the coolant in the engine. Once the coolant reaches the temperature (180°F in this case), it begins to open. Yes, the temperature can then begin to regulate. The thermostat doesn't ever fully open if it doesn't have to. Thus you don't get "constant opening and shutting and temperature spikes" as you're trying to state. If your coolant temps are up near 212, then yes your thermostat is likely fully open and you're not getting enough cooling. But under normal operation, this shouldn't happen if the thermostat (and other parts) are working correctly. There is no computer that controls the thermostat. No electronic cables attached to it. No vacuum lines attached to it. It remains shut until the coolant inside the engine reaches the temperature required to activate the thermostat. It is a very simple device.

The 136° which is happening is a result of uncontrolled flow which happens when the thermostat is stuck open. The engine will either never get up to proper temp, or it will take a very long time to do so.

 

damn so much knowledge im learning alot!

 

If you are running 212, your work is exceeding your cooling capacity. The cooling system isn't just some magic system that can take away all heat. If you're towing, rock crawling at low speeds in the 110° heat, etc, your cooling system won't be able to keep up. This is why you see threads about converting from mechanical fans to electric fans that run independent from engine RPM.

Again, as stated several times, the thermostat is NOT the only part of the cooling system. But the OP is not experiencing overheating, he's experiencing an inability to come up to temperature which tells me the flow is not controlled.

 

The thermostat has wax in it that expands when it warms up and this pushes it open, and it opens more the hotter it gets. It's not precise and the engine will adjust to a range of temperatures, but the engine works best around or above 180°F.

Even if the thermostat is closed the water pump circulates coolant past the the back side of it, so it will open when the coolant inside the engine warms up.

If the thermostat is stuck open the engine may never warm up completely because the radiator fan is always on driven by the engine, so cool coolant from the radiator is continually being drawn into the engine. It's as if you installed a thermostat with a 140°F temperature rating.

It's easy to test the sensor. Just measure the resistance across the 2 terminals and compare to what it should be at that temperature. Someone can post those values. You might be worse off replacing a perfectly good Toyota sensor with a cheap aftermarket part. And it's easy to get the 2 sensors confused, one that the ECU uses and one for the gauge.

 

Yes, exactly, thank you.

 

I stated at numerous points that the engine either won't reach operating temperature or will take much longer. P0128 is because the engine was not reaching full operating temperature. The examples given where the coolant is at 212 involves either a part of the cooling system not working properly, or abnormal driving circumstances, such as towing, off-roading in the heat at low speeds, etc. OP is operating under normal circumstances. Therefore, the engine is not getting up to temperature. There is a threshold which is ideal for the engine, which I also have stated previously. It isn't an exact science, but engineers have a pretty good idea. Overall the cooling system in vehicles hasn't changed a ton because it is a simple system that works. I don't know how much more I can explain it to you.

 

So what you're saying is you paid no attention to the subsequent posts where I stated on several occasions that it will either never reach operating temperature, or take a long time to under normal conditions.........

In this case the thermostat would probably still open in hot water, unless of course it is stuck at full open in which case it would already be open. He isn't overheating, but it isn't closing fully. At least based on the information I got from this.

 

Here are THREE posts which I stated it. Yes, including the most recent one.