Suggestions to seal a new thermostat switch in manifold - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OUbesto · 09-20-2020, 04:44 PM

Guys, with the help from this forum I just installed a new Champion aluminum radiator with dual electric fans. I installed the thermal switch (185/170) that I purchased in a relay kit for the fans. The instructions recommended not to use any thread sealant because it may interfere with making a proper and consistent ground. I also read somewhere on the forum not to crank down too hard. Unfortunately I still get a small amount of coolant leaking around the threads. Anyone have suggestions to stop the leaking?

**Warrens69GMC** · 09-20-2020, 04:47 PM

Take a marker, mark where it tops out at the manifold, then use teflon take for 3 threads past that line.

OUbesto · 09-20-2020, 04:49 PM

ok, will give it a go!

truckster · 09-20-2020, 06:07 PM

I would not use teflon tape for that application, as you need to ensure electrical continuity for the switch to work. I would use a gasket sealer - my preferred sealer is Permatex Aviation Form-A-Gasket.

**RodnRudy** · 09-20-2020, 06:21 PM

I had the same problem when I installed the temp sensor in the left cyl. head. I used Permatex thread sealant and no more leak and the gage reads just fine.

OUbesto · 09-20-2020, 08:25 PM

Quote:

Originally Posted by truckster

I would not use teflon tape for that application, as you need to ensure electrical continuity for the switch to work. I would use a gasket sealer - my preferred sealer is Permatex Aviation Form-A-Gasket.

About how much sealant should I put on the threads?

truckster · 09-20-2020, 09:01 PM

Quote:

Originally Posted by OUbesto

About how much sealant should I put on the threads?

Just wet the bottom three or four threads. Then you can wipe off any excess on the exposed threads.

gmc684x4 · 09-20-2020, 09:08 PM

I use 3 to 4 wraps of teflon tape 30 plus years no leaks no gauge issues

Need to insure both sending unit and npt port are clean and free from corrosion

The threads cut through the tape make continuity and the tape seals the gaps between the low points on the threads sealing it in

Old broken record wives tail dont seal the threads

The only time you dont seal the threads is when there are other mechanical means of sealing example Flared fitting on a brake line

Search the board this comes up about every 3 months

OUbesto · 09-21-2020, 09:52 AM

Thanks guys, I'll try both methods!

09-20-2020, 04:44 PM	#1
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	Suggestions to seal a new thermostat switch in manifold Guys, with the help from this forum I just installed a new Champion aluminum radiator with dual electric fans. I installed the thermal switch (185/170) that I purchased in a relay kit for the fans. The instructions recommended not to use any thread sealant because it may interfere with making a proper and consistent ground. I also read somewhere on the forum not to crank down too hard. Unfortunately I still get a small amount of coolant leaking around the threads. Anyone have suggestions to stop the leaking? Attached Images __________________ 1970 C-10 CST, LWB, 402/400, A/C

09-20-2020, 04:47 PM	#2
Warrens69GMC Registered User Join Date: Jan 2003 Location: Safford,AZ Posts: 3,625	Re: Suggestions to seal a new thermostat switch in manifold Take a marker, mark where it tops out at the manifold, then use teflon take for 3 threads past that line. __________________ 1969 307, t350 1950 Chevy Wagon 1978 Big 10 1967 C10, 250,3-OTT

09-20-2020, 04:49 PM	#3
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	Re: Suggestions to seal a new thermostat switch in manifold ok, will give it a go! __________________ 1970 C-10 CST, LWB, 402/400, A/C

09-20-2020, 06:07 PM	#4
truckster Registered User Join Date: Jan 2001 Location: Orem, Utah Posts: 7,982	Re: Suggestions to seal a new thermostat switch in manifold I would not use teflon tape for that application, as you need to ensure electrical continuity for the switch to work. I would use a gasket sealer - my preferred sealer is Permatex Aviation Form-A-Gasket. __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson

09-20-2020, 06:21 PM	#5
RodnRudy Senior Member Join Date: Oct 2014 Location: New Palestine In Posts: 932	Re: Suggestions to seal a new thermostat switch in manifold I had the same problem when I installed the temp sensor in the left cyl. head. I used Permatex thread sealant and no more leak and the gage reads just fine. __________________ Phil "Money is only a tool to create and achieve what you want most in life" PayPal: rodnrudy@comcast.net

09-20-2020, 09:08 PM	#8
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	Re: Suggestions to seal a new thermostat switch in manifold I use 3 to 4 wraps of teflon tape 30 plus years no leaks no gauge issues Need to insure both sending unit and npt port are clean and free from corrosion The threads cut through the tape make continuity and the tape seals the gaps between the low points on the threads sealing it in Old broken record wives tail dont seal the threads The only time you dont seal the threads is when there are other mechanical means of sealing example Flared fitting on a brake line Search the board this comes up about every 3 months

09-21-2020, 09:52 AM	#9
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	Re: Suggestions to seal a new thermostat switch in manifold Thanks guys, I'll try both methods! __________________ 1970 C-10 CST, LWB, 402/400, A/C



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