coolant leak...from around bell housing

1991 Lincoln TownCar 4.6 L.

Have infrequent coolant leak from the back ( toward rear of the engine block ) and around the transmission bell housing.

I have not figured out any particular pattern for when this occurs...short trips or after many hours of engine running from a trip.

No leaks from the hoses, rad or overflow tank areas...relatively new thermostat..
Clean coolant...with high percentage antifreeze...

Can not find anything in manuals about " trouble shooting " this type of coolant leak.

Worst guess is a " head gasket " leak that is not constantly leaking.
I tried a coolant " leak " fix material for head gaskets (Bar's Leaks...Block Seal...Liquid Copper )...but after a few days...the leak was back...

As a daily, urban usage driving to/from work....it's fine for 4 or so days....then bang.

I have been checking the coolant and oil levels every day...but still have not found
a " wonderful solution "....without a major engine head exam...

All thoughts and suggestions welcomed...

No oil in the coolant recovery tank? The block leak stoppers are not good for our 4.6L. The modular engines are made differently from the older style engines, and stuff like Liquid Copper and Bar's Leak will clog some of the smaller passages.

Try using a bright light and a mirror to trace exactly where it is leaking at. If it at a joint or gasket area, it will mean a teardown. It may be coming from a sensor back there. I had one years ago that had a busted diaphragm inside and leaked coolant only when it got hot.

Best of luck.

Hi Jdmeaux:

Thanks for the time and experience you share....very helpful.

No oil in the recovery tank....just coolant.

I'll try the mirrow and light suggestion after " lifting " the vehicle.
It's just a puzzle to not be able to figure it out....since it's not a simple hose,
constant leak visible source or cause-effect pattern.

I'll just have to continue to " track " it down.

Thanks again for your insights.

Most auto stores sell coolant leak dye that you put into your radiator and then use a black light to find it.