Hello all, first let's start with what happened...

Thermostat housing cracked/leaking so I decided to replace it. Upon removal of the three bolts that hold the housing to the block (is it the block or lower intake) one of the bolts snapped off. I attempted to drill, heat, freeze, just about every type of trick you could to get it out, I ended up taking it to a machine shop that upon second thought was a horrible idea. (Just very lackluster service and workmanship).

At this shop they drilled out the bolt and helicoiled it and gave me a new bolt. I know this knew bolt is standard compared to the metric size it used to be.

6 months later I am still leaking coolant, at first it was the thermostat gasket, then a radiator hose, now that everything is pretty much settled I'm still using coolant. Not enough to have a drip but enough to smell it when the engine gets warmed up.

I was at a loss.

So I added some UV dye to the coolant and after a few minutes of letting it run I found the leak! It looks like the seal I used from housing to block was giving way, so I used the seal in addition to some gray rtv and it did the trick. But now somehow the coolant is leaking up through the bolt I think. The system pressurizes the hoses and if I squeeze the hoses I can't see any running coolant. Weird.

I'm at a complete loss at what to do from this point. Do I let it ride and just fill it up with water? Do I switch out the engine so I have a proper torqued bolt with correct size?

What would you do?

 

The 4.0L OHV and SOHC engines are known for lower thermostat housing failures.
They usually split seams, or the older style housing leaks from it's threaded sensors.
If you are unsure, rent a coolant pressure test kit with a fully refundable deposit. GL

http://bengrosser.com/howto/fordthermostat/

 

Thanks for the posts on V6~4.0L~SOHC engines & TStat housings; good reference info.
Replaced the old leaking FRPlastic TStat Housing with a new Aluminum TStat Housing
in 2019Aug on a 2001 Ford ExSportTrac; no leaks as of 2020Mar after ~5K more miles.
My full write up with pics on that repair:
http://2001fordexplorersporttrac.fandom.com/Coolant_ThermoStat_Housing

 

Mis-posted reply. Please delete.