The MGA With An Attitude

On 3/22/2011 Doug Schimke wrote:
"What are the treads on the temperature sensor that screw into the engine"?

Thermal sensor bulb

This question comes up often enough to merit its own web page. And the answer is:

A pressure tight seal requires a sealing surface either before or after the threads, as the thread itself does not seal. The temperature sensor bulb seals between the flanged collar on the bulb and a mating machined shoulder in the bottom of the port, so it does not need any other sealing device.

Always use a flare nut wrench for this device so you won't damage the nut. The nut cannot be replaced without breaking the fluid pipe or disconnecting the soldered end connection. Repairing the pipe and replacing the volatile fluid inside is an expensive repair.

Senders for Smiths Temperature Gauges
Mechanically operated temperature gauges come fitted with a flexible capillary tube leading to a copper bulb. There are two types, but both are supplied with an adapter which provides a 5/8" UNF male thread for screwing into the block. (Click for larger image).
Thermal sensor bulb drawings

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