Sump plug thread size?

[Merlin 2]

Hi all

I am looking to fit a smiths oil temperature gauge that I have and was wondering if anyone knew the size and pitch of the sump plug thread so that I can get a temperature sender unit to replace the sump plug or an adapter to fit the sump plug hole that a smaller temperature sender can fit into.

before you ask why - I have a smiths gauge fetish - I know but I can't help myself - lol

[bmcecosse]

Don't do it! The sump plug is at the lowest point - a temp sensor (which is quite unnecessary anyway) will be ripped off all too easily that low down. You don't need to know the oil temperature. If the car is for road use - it will be fine. If it's for competition use - it NEEDS an oil cooler - Simples !!

[Merlin 2]

Its perfectly fine on the Mini and that's far lower to the ground and a much faster car. Have you ever seen a sump plug on a minor that is scratched up from coming into contact with the ground - other than after suspension failure?

[bmcecosse]

Indeed I have - and the sump well scraped up too - on my own car... Why on earth are you worrying about oil temperature???

[Merlin 2]

Have you not missed the point. I have the gauge and wish to fit it. just like I have a 5-speed gearbox and wanted to fit it. In the mini community everyone has a completely different car because everyone has their own preferences. I am the same with the Minor. I am going for the same sort of look with the Minor as the Mini - to the average joe it looks like it could have left the factory that way but there are quite a few differences that will make every day driving a little easier. If you want another way of putting it I want to fit the gauge because I can.

BTW what on earth were you doing to wreck the bottom of your sump?

[bmcecosse]

Carry on regardless - it's your car - I'm sorry - I don't know the sump thread..... Just driving over white roads - at speed...

[philthehill]

The sump plug thread is 1/2" x 20TPI UNF.
I totally agree with BMC but it is your car and you can do as you like with it but please do not come back and complain about the total loss of oil and engine damage because the temp gauge transmitter has been knocked off the sump because we will reply with the refrain 'we told you so'.
It would be better and much safer to fit an in line oil temp gauge adaptor, available from good motor sport on line shops for about £30.

[MikeNash]

Ooooh! someone else with an oil temp gauge that I'll be able to compare figures with!

Mine (a Smith's gauge like yours but so old it reads Fahrenheit) has a nut behind the capillary bulb that I'm fairly sure is a BSP thread. I took it along to local plumber stores (Woodstock Plumbing and Heating Supplies, Andover) who sold me for next to nothing a union that fitted it. This, I soldered into the sump next to and slightly up from the sump drain plug. In this horizontal position its about one inch higher than the sump floor and a little above the chassis leg base, and so pretty safe. (Other things are lower like the lowest part of the clutch mechanism, the sump base and the bottom of the oil filter. The number plate is, of course, much lower.)

Its been there for a few years without any trouble - so go to it and enjoy yourself and let me know what you see! I think you'll be surprised, Mike Nash.

[bmcecosse]

That's a much better idea - well done Mike... If you don't want to spoil the fun on here Mike - can you PM me the temp readings you get, please??

[philthehill]

The sump plug is not at a right angle to the side of the sump it points down so any extension fitted to the sump plug hole will come below the bottom level of the sump and that is the problem.
Raising the position of the transmitter above the bottom of the sump and making it at a right angle (horizontal) to the side of the sump is a much better idea and I will go along with locating the transmitter in that position.

[bmcecosse]

Exactly.......I wouldn't give it a month with the speed bumps (and pot holes) we have up here......

[Merlin 2]

The sump plug thread is 1/2" x 20TPI UNF.

Many thanks for that. I have had to remove the sump anyway as it appears there is a leak from somewhere so I may investigate getting a mounting in the side of the sump seeing as it is out anyway. I hope the leak is just a gasket as its a 1275 ital engine and getting a replacement sump is a little more difficult than the stock 1098 engine sumps.

[Merlin 2]

That's a much better idea - well done Mike... If you don't want to spoil the fun on here Mike - can you PM me the temp readings you get, please??

You don't need to know the oil temperature. If the car is for road use - it will be fine. If it's for competition use - it NEEDS an oil cooler - Simples !!

Why on earth are you worrying about oil temperature???

Hhhhmmmmmm!!!!!!!!

[bmcecosse]

The leak won't be the 'sump' - most likely the end seals, OR the crank tail labyrinth if there is pressure in the crankcase. My request for info re oil temps was merely to confirm they are nothing to worry about..

[MikeNash]

Mr Merlin,
I've been making the assumption that your Smith's gauge is the type with an ether(?) filled bulb, a capillary tube ending with a pressure gauge on the end which is calibrated to show a temperature - is that right? It's not an electric type, is it? That might be more suitable to be fitted as you originally suggested.
Might I suggest that if you leave the sump plug unmodified that you drill it on the inside and araldite in a small bar magnet?
You'll be amazed (and pleased) at what it captures and retains.
Regards, MikeN.

[bmcecosse]

Just put the magnet (neodymium is best and cheap as chips on ebay..) on the outside of the oil filter casing.

[Merlin 2]

Mr Merlin,
I've been making the assumption that your Smith's gauge is the type with an ether(?) filled bulb, a capillary tube ending with a pressure gauge on the end which is calibrated to show a temperature - is that right? It's not an electric type, is it? That might be more suitable to be fitted as you originally suggested.
Might I suggest that if you leave the sump plug unmodified that you drill it on the inside and araldite in a small bar magnet?
You'll be amazed (and pleased) at what it captures and retains.
Regards, MikeN.

Thanks for the ideas. It is an electrical gauge not the capillary tube type. I might have to leave it for a bit before I get round to it now as I just need to get the car on the road now as my daily driver car is hanging on for dear life. All I have left to do is the front suspension and the braking system before an MOT. Its been a long journey I don't think I have ever worked on a car that has fought so hard not to be restored.