Leaking drain plug on Universal M35 diesel

[sailingdeacon]

First, let me say I am stupid when it comes to engines. I have a very slow leak at the 1 1/8" (1 1/4"??) diameter engine fresh water drain plug. It has a smaller plug within it, but does not seem to be leaking there. If I back it out a small amount and put polisulfide caulk on the threads and tighten back up, would that fix it? Or is there too much pressure. Or am I into something more involved. By the way I am only hoping I can unscrew the plug.

 

[sailingdeacon]

no problem....

After getting the 1 1/4" socket, it unscrewed easily. I backed it off a little pressed in some boatlife caulk so we will see if that works. if not, then I'll drain the antifreeze and apply pipe tape.

 

[chaco]

Engine Sealants

As you want to fix this leak for GOOD, you will need to remove the plug
and apply high temp silicone sealant (I use gray gasket sealer rated for 250F)
Boatlife Caulk is designed for cabin leaks and low temp thruhulls (not engines).
Clean the threads with a wire brush and wipe clean with carb cleaner.
Make sure everything is REALLY dry and clean prior to sealant application.
Apply the sealant to drain plug and engine block.
Replace drain plug and wipe off excess sealant.
This will also be a perfect time to flush your fresh water cooling system prior to plug removal. Replace coolant with 50/50 water-antifreeze mix.
All this will make sure your coolant doesn't leak and engine overheat when
you really need it !
Good Luck !