Water Temp. Sensor Threads

[jjkuzman]

Does anyone happen to know the thread size for the sensor? I found some 3/8 BSPP and BSPT fittings, but they do not appear to be the correct size. Thanks.

[Charlie Tolman]

Temperature sender thread size:

The threads in the cylinder head are very close to 3/8 BSP and also 5/8� x 18. This BSP size has 19 threads per inch, according to a catalog.

These two thread sizes are so close, that it is hard to tell the difference. A 3/8 BSP fitting will be slightly loose in a 5/8� x 18 hole, and a 5/8� x 18 fitting can generally be started in a 3/8 BSP hole, but it will become tight within a turn or two. My measurements indicate that the 5/8� x 18 thread diameter is about 0.004� larger than the BSP threads.

I have a 12G-206 head, and the standard factory plug fits very nicely. A 5/8� x 18 bolt becomes tight within a turn or two. The standard plug is slightly loose in a 5/8� x 18 nut.

Therefore, the thread size in the head most likely is 3/8 BSP.

Charlie Tolman

[Charlie Tolman]

To add confusion to the problem, a 3/8 NPT (tapered thread) with 18 threads per inch, has an average thread diameter that is somewhat close to the other thread sizes mentioned above. This NPT size is not usually used for mechanical temperature bulbs (senders).



Charlie T.

[floridamary4]

thanks for sharing

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