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[iliak]

Hi!
Had my radiator replaced, took both thermal switches off the old radiator and put it on new one. Didn't use any sealant, my hope was that copper washer is enough. Seems like it isn't. There's small leakage on thermal switch (the one on the bottom). Not a big trouble,  but it's irritating.
The question is: what torque should I have used on them thermal switches? Couldn't find this info.
Thank you!

[Doctor Gollum]

I tend to nip them up, but don't over do it or you'll crack the plastic

[iliak]

Yeah, that's what I was afraid of, to crack the plastic 

[Nick W]

Did you replace the washer? If not, it's probably flattned and work-hardened, and therefore not sealing.

[iliak]

> Did you replace the washer?

Sure. Not original, though (JP Group or something). Original is so much expensive.
Yes, this may be the reason. Original washer maybe is made of softer copper.

[Andy B]

try a few turns of PTFE tape on the sensor's thread

[Andy H]

I use blue Hylomar sealant.

If I have to use PTFE tape on plumbing in the house it seems to take masses of tape and quite a lot of force to drive the tape into the screw threads to get a seal.

The thermal switch is designed to seal on the flat face of the radiator - not the thread in the insert. The ideal seal would be one of those washers with a rubber insert - I think they are called Bodok seals (but maybe that is just the ones we use on hospital Oxygen bottles )

[Andy B]

I use blue Hylomar sealant.

If I have to use PTFE tape on plumbing in the house it seems to take masses of tape and quite a lot of force to drive the tape into the screw threads to get a seal.

The thermal switch is designed to seal on the flat face of the radiator - not the thread in the insert. The ideal seal would be one of those washers with a rubber insert - I think they are called Bodok seals (but maybe that is just the ones we use on hospital Oxygen bottles )

I know PTFE isn't the proper fix, but the OP has a leak that the PTFE would probably sort.
Sounds like you're putting too much tape onto your threads 
Dowty seal is the word you're looking for 

[iliak]

Thanks guys    Since nobody seems to know proper torque for these sensors, the only option is sealant, I think.
Not today, though. It's too damn cold out there 

[steve6367]

Thanks guys    Since nobody seems to know proper torque for these sensors, the only option is sealant, I think.
Not today, though. It's too damn cold out there 

I imagine the required torque would be almost impossible to measure anyway - when I have done them new washers, ptfe on the thread and go very gentle - hand tight and small nip. The radiator is not strong there.

[tidla]

I has liquid ptfe in a bottle in my tool box. Use it for truck air line seals. Easier  to use than the tape and has excellent sealing properties even on low torque applications. Thats my two pennies worth.