Damn temp sender leak

[AJs72K5]

OK guys, need some help here. Been fighting a coolant leak on the driver side temp sender. I mention driver side because the passenger side has one too, but for the FAST EFI...driver side is for the autometer gauges and is the only one leaking.

I've been using Permatex thread sealant...basically teflon paste, but it's just not holding. Is there any reason I can't use this stuff? It says it's sensor safe and coolant resistant:

http://www.permatex.com/products-2/...er-pump-thermostat-rtv-silicone-gasket-detail

Open to ideas...

 

[bp71k5]

I use the Teflon stuff on a couple sensors. Are you sure it's leaking from the threads and the sender isn't cracked or damaged?

 

[AJs72K5]

Pretty sure it's coming from the threads

 

[bp71k5]

Maybe it's tapped for NPT and the reducer bushing you got is different thread? It's strange that the correct threads would leak that bad. Maybe the same place made my radiators made your sensor.

Is the joint between the sensor and reducer leaking or at the manifold/reducer fitting? You might try removing the sensor and plugging it to narrow down which part is actually leaking.

 

[76zimmer]

good root cause ideas bp!
I use 3 full wraps of teflon tape, then the sealant, and have very good results with that.

 

[AJs72K5]

Joint between sensor and reducer is good. Definitely leaking at the manifold / reducer joint. I'll pick up another bushing today.

 

[ryoken]

is that bushing bottoming out?






we use aviation sealant religiously on all our NPT stuff in the boats...

 

[AJs72K5]

is that bushing bottoming out?






we use aviation sealant religiously on all our NPT stuff in the boats...

It's not bottomed out Paul. The pic makes it look like it, but there's two threads still exposed. I'll see if I can find some of that stuff.

 

[ryoken]

the super 300 also works very well.. has a bit more "body" than the aviation seal..


http://www.permatex.com/products-2/...ex--super--300--form-a-gasket--sealant-detail

 

[Fordum]

Remember, everybody always worries about getting a ground for the sensor if they use teflon tape or other sealant, with some reason.
If you get the sealant thick enough and it does not let it get grounded, then the sensor will not work.
Most of the time, even with lots of sealant, there is at least one small place where the metal touches enough to give the small amount of ground necessary.

However, a leak really needs to be stopped. Once you have done that, if you find out you have lost your ground, you can work up an external ground to the body of the sensor with some wire.
So, worry about the leak, then about making a good ground contact.

 

[ryoken]

I've never had sealant "not" ground on NPT... but I have seen Teflon tape do it..

 

[Fordum]

Yep, I love Teflon's electrical insulating properties. In my field, heat transfer without electrical connection is vital.
Mica is still king, I think, for thinness with electrical resistance, but some of the Teflon derivatives can be compressed just as thin and still handle fairly high voltages, transfer more heat and be flexible.