Low coolant temp reading

[Jobi-Wan Kenobi]

Are there any common issues with the coolant temp sensors on these engines?

I thought I was having an issue with my engine not reaching normal operating temp. My gauge wasn't showing normal temp and I verified temp by looking to see what was being broadcast with a scan tool just to make sure the stepper motor for the gauge didn't fail. The system was topping at 177.8F. So that said to me a bad thermostat. I replaced it today but that didn't fix the issue.

This is the thermostat I put in. Starting to open temperature is 187F. And even before this coolant temp was reaching over 195F.

https://www.napaonline.com/en/p/THMPM1876545

 

[Tonyrodz]

Are there any common issues with the coolant temp sensors on these engines?

I thought I was having an issue with my engine not reaching normal operating temp. My gauge wasn't showing normal temp and I verified temp by looking to see what was being broadcast with a scan tool just to make sure the stepper motor for the gauge didn't fail. The system was topping at 177.8F. So that said to me a bad thermostat. I replaced it today but that didn't fix the issue.

This is the thermostat I put in. Starting to open temperature is 187F. And even before this coolant temp was reaching over 195F.

https://www.napaonline.com/en/p/THMPM1876545

It's possible you could've got a bad t-stat out of the box. I've gotten new parts that were bad before.

 

[mattbta]

what radiator are you running?

 

[Fless]

How long as this been going on? Any changes prior to the issue, like a new radiator or other maintenance?

 

[rockola1971]

With a cold engine your thermostat should be closed. The thermostat being stuck open would cause your low engine temp when it shouldve warmed up to near 200deg. You can verify your thermostat is not stuck open by starting the engine up and squeezing the upper radiator hose between your thumb and forefinger. If the thermostat is stuck open you will feel water flow pressure push outward against your fingers and the upper radiator hose will go rigid or pop the radiator cap on a cold engine and start it up. If you see flow in the radiator then your thermostat is stuck open.

Im leaning toward your engine coolant temp sensor which is what tells the gauge what the engine temp is, is bad or has a loose or corroded connection.

 

[Marky Dissod]

Other possibility is that your radiator's 3rd orifice is slightly wider open than it should be.
Rule out the other possibilities FIRST.

If you decide to get rid of your radiator, sell it to someone who can use that radiator as is,
like someone who tows / hauls REALLY heavy, or a hardcore racer.

I've been dreaming of a radiator whose 3rd orifice size could be physically calibrated to individual taste.

 

[Fless]

With a cold engine your thermostat should be closed. The thermostat being stuck open would cause your low engine temp when it shouldve warmed up to near 200deg. You can verify your thermostat is not stuck open by starting the engine up and squeezing the upper radiator hose between your thumb and forefinger. If the thermostat is stuck open you will feel water flow pressure push outward against your fingers and the upper radiator hose will go rigid or pop the radiator cap on a cold engine and start it up. If you see flow in the radiator then your thermostat is stuck open.

Im leaning toward your engine coolant temp sensor which is what tells the gauge what the engine temp is, is bad or has a loose or corroded connection.

There's probably no radiator cap with the surge tank system, so no way to view flow in the radiator.

 

[Jobi-Wan Kenobi]

Yea the possibility of the new thermostat being bad does exist. But even with the new thermostat system is still reading a max temp of 177.8F, the same as what I had before changing. I'm also not having any issue with interior heating (it's 16F here right now). So I got to wondering about the sensor, or even the circuit.

The radiator is I believe the factory original. No maintenance to the cooling system has been recently. This just started Monday morning when I was driving to work.

 

[Fless]

I can't tell from the thermostat pic if it has a jiggle pin or not. If it does have one, it should be oriented at the highest point of the thermostat, as installed.

 

[Jobi-Wan Kenobi]

It does have one. I'm not sure about the orientation though.