Coolant Temperature Sensor Threads
 

Hi all,

So...I messed up the threads on my coolant temperature sensor by over tightening it, I backed it out with the messed up threads.

Now I can't thread the sensor in at all, but the threads seem to be there.
I think they're pipe threads.

I'm going to stop by the auto store tomorrow to look for a tap. I think this might work well enough if I can find the size I need. What pressure does this need to withstand? Would a few threads and some sort of weak (removable) adhesive work?

Any ideas?

So which is messed up? The threads in the head or the threads on the sensor? Don't know if it is a pipe thread or not, but it probably is. You most probably need a hard ware store not an auto parts store, but maybe not. If it is the head, you need a tap, if it is the sensor you need a die, point on either might be if it is a sensor buy a new one. It is also probably damaged and might be cheaper than a die. As to a removable sealer? Sounds nice but, I do believe the sensor depends on an electrical contact between itself and what it is screwed into in order for it to work, thus if you use a teflon sealer for Pipe Threads commonly found in plumbing section as a tape dispensor it is altogether possible the sensor will quit working anyway as teflon can act as an insulator too!
The moral? Righty tighty lefty loosy a ditty to remember which way to tighten things does not mean hog it down with the strength of a gorilla.

First issue - galled threads in an aluminum casting are a class one bit-h to clean up, even with a chase tap. Use tapping oil and CAREFULLY run the tap down the threads. Clean off the sensor threads, and use your bare fingers to check for smoothness (threads can be sharp). If you find burrs or areas on the sensor that are bad, bite the bullet and get another sensor.

Teflon tape is a godsend in this application, but make sure the tape is on the threads only. The sensor tip is exposed to the water flow/temperature, so the use of tape won't mess up the reading. As for pressure, it shouldn't exceed 30 pounds, and should be much less.

The ultimate repair is to insert/install the correct Helicoil. The hard part is finding the right one. Installing is easy.

All fixed
 

I ran a tap gingerly down the threads and bought a new sensor for a total of $22 of extra expense. It was 1/8 pipe thread.