Fan switch coolant leak

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Just assembled a new radiator and fan switch from reputable supplier. I was able to fit a 1-1/8" wrench over it to tighten the switch by hand. I have a persistent coolant leak at the switch when filling the radiator. The switch came with an aluminum washer but nothing rubber or fiber. Any tips how to prevent a leak? Should I have added teflon tape, or pipe dope, or loctite to the threads?

[18Fiatsandcounting]

The aluminum washer should be all you need to prevent leaking at the switch. Teflon tape or thread sealer could help, but it shouldn't be needed.

I'd take it out and inspect all the mating surfaces (radiator, washer, switch). I don't recall a torque value for the switch, but it shouldn't be insanely tight. You could try a copper washer in place of the aluminum one.

And you're sure the leak is from the switch and not from somewhere else?

-Bryan

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I think I simply didn't have it tight enough. Rookie mistake. My issue was a) ignorance...influenced by learning to not go very tight with bolts on this car... I was afraid of overtightening the switch, and
b) not having the right tools...my auto universe is 100% metric but no 29mm, only a shallow 1-1/8" socket which didn't grip well... I picked up a 1-1/8" closed-end wrench and suddenly had newfound leverage. Watching for leaks now but nothing in ten minutes, I think I'm good.

Adding a note for anyone with a similar issue, I did forward my question to Autoricambi and Csaba explained the metal washer seals against a perfectly flat surface on either side, if there is a leak with proper tightness then there has to be some irregularity with the surface flatness.

[18Fiatsandcounting]

Great, glad to hear it appears to be fixed!

I don't know if you have an Autozone store near you, but I just picked up a 29mm socket on sale at the store in my town. $5, which is a pretty good price for a deep impact metric socket. They had most of their metric sockets on sale.

-Bryan