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MG MGB Technical - Early temp sensor nut

Hi all,
the temp sensorīs nut on my MGB-69 is heavily rounded out from using all types vice grips, but at first I am happy to have it loose and out.
The next question is now: how to repair the nut and how to get at least 2 nice flats on it to screw it in again?

Terrence Goodell wrote in 2002:
Once you separate the nut from the sensing bulb, you can weld more metal on the flats and file them down to get your nut back in shape. But you definitely don't want to weld anywhere near the sensing bulb.

Ok, I can remove the nut from the bulb, but not from the tube, which holds ether in it. As the gauge still works nicely, I donīt want to through it out.

Any idea for a possibility to get the nut in shape again?

regards Walter


Walter Prechsl

You don’t have many options. You could try filing some flats on it, to fit a slightly smaller spanner.

Thoroughly clean the threads and use plenty of anti-seize when refitting.
Dave O'Neill 2

Having spent far too much time with that fitting quite recently I'd say other than what has already been put why not leave it as it is and just do not use vice grips on refitting. Once fitted you hopefully should not need to remove the nut for a long time.

Check where the probe fits in the head and the threads are clear and clean. Clean the matching mating surface on the probe and the base of the nut union. Once the nut bottoms out it does not need to be overly tight.

Stick with your gauge as the new ones are not as good, certainly not in my fairly recent experience of the dual gauge.
Nigel Atkins

Or just put back with grips.
paulh4

Thanks for your hints!

As I donīt like botch, I want to repair it somehow. Maybe itīs an idea to protect the little tube inside the nutīs hole with some tin sheet or roll and weld the nut on, at least for 2 flats?

Walter
Walter Prechsl

I can't remember how or not congested the area around where it fits is, if you just do two flats will you get a tool on it to easily tighten the nut fully up as it turns it all directions (if you follow me) otherwise the grips/pliers will be out anyway.

It's your part and car you can do what's best for you.
Nigel Atkins

You might get away with two flats.

Dave O'Neill 2

Blimey, you only need one flat!
Nigel Atkins

Walter
How would you go if you got yourself a suitable reducing bush something like the pictured and cut a slot lengthwise with a cutting disc ,just wide enough to allow it to be slipped over the tube
I'm pretty sure the thread is 5/8" unf on the A2 type bulbs so should be readily available from a plumbing shop--stainless steel would be the go, nice and strong---The slot wouldn't effect sealing as the sealing is done between the bulb and the cylinder head
then cut the old nut off-

willy

William Revit

Willy,I like your idea!
. . . and I will do that, thanks very much
Walter Prechsl

Or use a 5/8UNF bolt, bore to suit on a lathe, machine the head down to the correct thickness, then cut a slot in it and slip over the capilliary.

Colin
Colin Parkinson

This thread was discussed between 06/12/2020 and 09/12/2020

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