A series heater sensor

[FranklinLeicester]

Hi chaps,
I am fitting a new temp gauge complete with it's capilliary and apadtor union. The kit came with a new brass union to screw into the cylinder head. Having taken the old one out, the new one didn't want to screw in easily. Not wanting to damage it I backed off and withdrew it. I wanted to compare the 2 items but the old one has badly flattened threads so although they look the same, I can't be certain. The new one has "5/8" stamped on it but the old one has nothing. What to do? Can anybody tell me what the thread in the head is likely to be as I fear I may have to seek out a special adaptor.
Thanks, Franklin.

[stevejgreen]

Re: A series heater sensor

The thread should be 5/8"-18 UNF

[lil_red_roadster]

Re: A series heater sensor

5/8 UNF - same as B series temp sender IIRC...but if you Google the various Mini sites you'll get all sorts of answers...e.g. 5/8 BSP, 3/8 BSP...the joys of the interweb. Have you got a thread gauge or tap set you could check it with..?
That man Green got there first..!

[FranklinLeicester]

Re: A series heater sensor

Thanks both, I'll put a 5/8th bolt up it to clear the thread then check what the "5/8th" on the union refers to.

[Robert in Cumbria]

Re: A series heater sensor

I have three senders and one 'A' series head they are all 5/8" 18 - UNF.

3/8" BSP is 19 tpi and ~36 thou larger than 5/8" UNF so they could be confused. Some older capillary temp gauges were 3/8" BSP.

[FranklinLeicester]

Re: A series heater sensor

Sorted. Having confirmed that the 2 threads were the same, 5/8 UNF, I had the courage to go for it. I had to clear a load of old Boss White out first. Thanks for your help. Franklin.