mildly curious coolant leak at fan switch in rad

[DanHoug]

in 2019 with entire rehab of the cooling system i replaced the rad with a new Behr and new rad fan switch. this past month noticed a leak at the rad switch, was able to tighten it probably 1/2 to 3/4 of a turn without stress. continued to leak.

yesterday i pulled the fan switch to see if the rad was cracked or what. the rad has a nice brass insert molded into the plastic side tank for the fan switch threads, no crack. but the supplied gasket around the fan switch was split and mushy, like you'd expect from paper soaked in water. came with the switch but it was red on both sides with gray in the middle. i had put a thin coat of RTV sealant on it when installed. it seemed like good quality at the time.

my fiber gasket parts drawer yielded an appropriate sized dark gray fiber gasket but again composed of 3 layers. this time i coated it with GasGaCinch, let it dry, and installed. no leak of course. i think GasGaCinch is the better choice over RTV as i wanted to seal the fiber material from the coolant.

i don't really want to put a copper or aluminum gasket in there as i want the sensor torque to be low against the rad threads and the rad to sensor sealing surface is plastic. fiber or probably nylon would be best, something with low durometer but coolant impervious.

anyway. something to keep an eye on with new rad fan switches.
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[Gizmoman]

Dan, possibly an o-ring would do it?
I'd try to find one that had to stretch over the threads a bit and apply some lube to both faces so it doesn't grab - just squishes.
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82 Vanagon Westy - AAZ 1.9 TD, HE200 Holset, WAIC, 27.75 dia tires, Electric power steering, 5-speed AAP w/.078 5th
Oversize spare carrier - stock location (no longer for sale).

[DanHoug]

o-rings need to be captive in a groove/recess in order to not squish out!

the treated washer will work for a few more years if not longer as it is a different composition. i'll keep my eyes open for a nylon one of the right diameter or just more hard fiber ones.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[Gizmoman]