flue sensor mount ejected from pipe?

catskilt

I was replacing the venturi on my triangle tube prestige solo 250 propane boiler when I noticed the threaded connector of the flue temperature sensor was fully off the exhaust pipe.
I have no clue how long this thing has been popped off!
What might cause this? pressure, heat, corrosion?
Should I attempt to re-attach the threaded mount, or will I need to replace the entire vent pipe?

catskilt

I did used to have some delayed ignition BANGS a few years back, until i replaced the igniter. Possible it happened back then and wasnt noticed because the sensor is behind the board

kcopp

Pretty sure that was held in w/ a rubber gasket.
You can get another gasket or I would clean up the vent pipe and then use some high temp silicone to hold it in place.

EdTheHeaterMan

Get some high temperature RTV silicone caulk and just put the sensor back in the hole as is. https://www.supplyhouse.com/Polymer-Adhesives-PSHT-T-Red-Polysil-Hi-Temp-Industrial-Grade-Silicone-Sealant-10-5-oz

OOPS they are out of stock
go to Home Depot and get this https://www.homedepot.com/p/Permatex-3-oz-High-Temp-Red-RTV-Silicone-Gasket-Maker-75152/302774959 Good to 650° and it is only 3 ounces, more then enough. Under $7.00

SuperTech

That yellow wire looks kinda crispy. Hopefully you didn't burn up the original rubber gasket that held it in place. 

mattmia2

Or the blowby from the missing gasket burned the wire.

EBEBRATT-Ed

Wires are crispy. You might be able to make a strap out of sheet metal to hold the sensor in addition to the silicone

tim smith

I am pretty sure Triangle has a flue sensor repair kit. That one did not have a grommet, it was pressed in and soldered. The repair kit has a large grommet to fit in hole the I think it’s a new sensor to go in grommet. They may also now just sell new flue outlet pipe, secondly, the rest of boiler will need good check over as flue gas may have caused bit of damage.
Good luck