Hi there, I'm looking at those aluminium radiators on eBay. Specifically because I'd like to put a temperature switch for an electric fan in the drain hole.
Does anyone know the thread size of the drain bung on their radiator? I understand that there may be more than one type so any info would be good.
Thanks,
Matt

Or
If you have put a temp switch in one of these radiators what model/temp range switch did you use?

The last alloy radiator I had was fitted with a 14mm drain plug. I am unsure if they are all fitted like this, but bnicho was able to fit a thermo switch to his alloy radiator with a 14mm plug.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Excellent, thanks for that.
I see that Tridon do a few M14 switches.
Strangely TFS 106 & 187 Are both 2 terminal N/O 95 on, 90 off. I can't see any difference.
Anyway thanks again.

Neither can I ...

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

would it not be better to have the switch at the top of the rad since the water at the bottom of the rad where the bung is has already passed through the rad and cooled, meaning if the water at the bottom of the rad is at 90 or 95 degrees, the motor has already boiled and the switch is cutting in too late to save it cooking? i assume the temp differential would have to be at least 10 degrees meaning you would want a switch that cuts in at a lower temp if u mount it in the bottom, or have a top tank mounted switch to better reflect the true temp of the water in the engine. i had a hole tapped in the top tank of an an alloy rad once before for a second temp gauge in a silvia, wasn't expensive to get it done by the radiator shop or u could do it yourself.

The water flows down as it is pumped from top to bottom, and yes the switch will come in if the bottom temperature proves there is not enough air through the radiator to keep the temperature down.

With the switch at the top, then the fan would simply stay on more. The temp at the top of the radiator is not proof that the radiator is cooling or not, just that the engine is hot. Its the bottom temperature that is important for water returning to the engine. If it is not cool, then the engine will boil.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

More radiators are M16 than M14.
I have a Tridon TFS123 in my car as its one of the closest matches to what rover put in the SPI cars originally.

Wise words Mick.
I guess my best bet would be to just get the radiator and then buy the switch as it seems the thread in the drain bung will not be the limiting factor.

12mm or 14mm shouldn't be a problem. If its 12mm and you need 14mm, just run tap through hole, its only 2mm, it should have atleast that much meat to work with.