I recently had to replace the timing belt and fan bracket on my truck (1990 Reg Cab DLX 4wd 3VZE). I installed a new Aisin water pump at the same time, but there's been an intermittent coolant leak since then. Coolant was clearly coming from around the water pump or thermostat housing, so I went back in and replaced the gaskets twice with no improvement. I finally used some dye and found the leak was coming from the factory plugged outlet for the oil cooler (which my truck doesn't have). I really don't want to go back in and pull the water pump yet again. Does anyone know of a way I could seal that plug without removing it? I thought about teflon tape, or soldering the hole. I even considering JB Weld but I don't think it would hold. I know I can get the pump replaced, but that would take a week and I need the truck sooner. But, I'm not so desperate that I'll try something that'll break in a few weeks/months. Any ideas? Suggestions?

 

That's a decent sized pipe, and it's pressed in.
My thoughts would be to either tap the hole and put in a bolt with thread locker, or fill the hole with melted down aluminum stick rod.
If that plug blows out completely it'd drain your system in seconds.