Teflon tape question - coolant system

I wrapped my water pump heater-in pipe threads with teflon tape, as well as the temp sensor threads on the thermostat housing.

When I removed my temp sensor to clean it, I noticed the teflon tape below the point of contact between the threads on the thermostat housing and the threads on the temp sensor was gone.

Is it normal for the teflon tape to disappear where it is in contact with the hot coolant?

Just curious really, is all.

Teflon tape doesn't have a lot of strength - and it's supposed to be worked into the spaces between the internal and external threads. I usually use Teflon paste, tho - it does't care which way you wind it, and it's easier to clean off later.

However, you may notice that your temperature sensor doesn't work properly anymore (is it a one-wire, or a two-wire?) One-wire sensors are self-grounding through the part they're screwed into, and Teflon can interfere with that (for self-grounding sensors, I'll use RTV Copper to preserve the ground, after cleaning the hole and the part.)

Two-wire sensors should be grounded through the wiring, but it's still a good idea to make sure the sensor body has a solid ground anyhow...

5-90

This would be the temp sensor in the thermostat housing, which I am talking about. It is the 2 wire deal for the PCM.

I didn't touch the one wire gauge sensor at the back of the block, and the gauge works anyhow.

Thanks fo the comments! I'll pickup some copper RTV, I never though about what you are saying in terms of the teflon tape blocking off the ground. But as this sensor is 2 wire I should be fine anyway. I hear that teflon tape is only really made to make it easier to screw the piece in (sort of like a lubricant) and then it will shread away......so I'd think you'd achieve a ground connection anywho.

Thanks again!

By the way the sensor probe with the two wire (the PCM sensor, not the gauge sender) might be insulated from the natural ground anyway. I'm not sure but I thought it looked like it....

Blaine B. said:

This would be the temp sensor in the thermostat housing, which I am talking about. It is the 2 wire deal for the PCM.

I didn't touch the one wire gauge sensor at the back of the block, and the gauge works anyhow.

Thanks fo the comments! I'll pickup some copper RTV, I never though about what you are saying in terms of the teflon tape blocking off the ground. But as this sensor is 2 wire I should be fine anyway. I hear that teflon tape is only really made to make it easier to screw the piece in (sort of like a lubricant) and then it will shread away......so I'd think you'd achieve a ground connection anywho.

Thanks again!

By the way the sensor probe with the two wire (the PCM sensor, not the gauge sender) might be insulated from the natural ground anyway. I'm not sure but I thought it looked like it....

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I've run into one-wires that quit working with Teflon tape - and were hit-or-miss with Teflon paste. They worked just ducky when I switched to RTV copper, so I keep some around. It not only works well on self-grounded sensors, but also holds up to help exhaust gaskets seal (I use it on manifold gaskets and converter flange gaskets - but not on the collector donut.)

Teflon more makes the part easier to take out than put in - and it also helps to seal up shonky threads (mass-produced threads can be problematic.)

The thermostat housing should still ground through the screws anyhow - there's metal-to-metal contact there, and with the underside of the screw heads to the housing. I'd suggest replacing those screws with stainless (should be able to find them at the local hardware store) or brass or bronze (if you have local access.) If you can't get any of those, you can use regular carbon steel and just smear RTV all over the thing (or even clear tub silicone - just clean it off and reapply whenever you have to remove the housing.) I've pulled severely pitted thermostat screws out of my rigs the first time, but not since...

5-90

No problem once again, but I was wondering. Could any bit of torn/shreaded teflon tape clog any of the cooling components like the thermostat, or get lodged in it somehow to make it stuck open?

Blaine B. said:

No problem once again, but I was wondering. Could any bit of torn/shreaded teflon tape clog any of the cooling components like the thermostat, or get lodged in it somehow to make it stuck open?

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Teflon tape is thin enough and friable enough that I'm inclined to not think so. I know you can have trouble using it on low-pressure hydraulics (I use either Teflon paste, LocTite PST, or LocTite 545 on pretty much everything I want sealed anymore...) but you don't have passages that small in the engine, save off the oil galleries (you definitely want to use PST or 545 on the pipe plugs in the back!)

As long as nothing can get out of the system, and everything works as designed, you should be all right. The only real "close-tolerance" parts I can think of would be the head gasket sealing surfaces and the water pump bearings and seals - beyond that, everything is pretty sloppy, relatively speaking.

5-90

I see. I'm sure it would probably even me blended further as it passed through the waterpump, even if any were to make it that far.

How many of you use teflon tape on sensors and stuff in the cooling system?

Blaine B. said:

How many of you use teflon tape on sensors and stuff in the cooling system?

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You already know my answer to that...:laugh3:

Blaine B. said:

How many of you use teflon tape on sensors and stuff in the cooling system?

Click to expand...

I used to use tape. Still do whenever Im out of the paste. Paste has seemed to work better IMO.