Howdy, I just had a Jasper engine installed and I've had to take it back to the mechanic twice because the gauge says it's overheating while the temperatures are actually all fine.

Today my mechanic told me that the temperature sensor hole on the back of the head has a smaller bore than the one on my old engine, and thinks the sensor is making direct contact with the head, resulting in a false reading. Says the sensor has signs of scouring.

He said he's going to add a nipple or something to fix the issue without having to warranty swap the engine but I've yet to see what his solution looks like

Is there any reason why this engine would have a smaller temperature sensor bore? Different year head? Needs a different model sensor?

It's a 96 4.0, Japanese import

 

It's a good chance it's a metric pipe thread. They are just different enough to be weird. You can rethread the hole with a standard pipe tap and use a lot of sealant.