My 1990 240 is slowly leaking coolant down the driver side of the block near the bell housing, just rearward of the PCV separator box.

It only leaks after the car has been driven for maybe 15 miles at least. I haven't been able to get it to leak just sitting idling but maybe I was impatient.

So here's my dilemma; I think the coolant is coming from the heater hose that is connected to the block just under the intake manifold between cylinders 3 and 4. However, I can't see in there without removing the intake manifold and obviously once that is off I won't be able to run the engine to create the leak to verify the source.

Any ideas how I might verify the leak source? It's been leaking slowly for about 1000 miles so there might just be an obvious trail leading right back to the source.

I do not have a pressure tester.