I have attached an image of the rear of the motor. It is probably the US version but close to our setup for RWD.
Do any bolts which hold the auto transmission to the engine block end up in the water jacket of the engine block and one of them is corroded through and giving the passenger side leak? Is there any coolant evident at the drain hole under the bell housing?
Is the head gasket failed, leaking without any loss of compression etc.?
Are all cylinder head bolts under the tappet cover?
For coolant to be going over the even bank side of the motor/transmission maybe it's "squirting" past the thermostat's pressed steel gasket.
In passing I have heard tell that there are welch/welsh plugs or freeze plugs under the lower inlet manifold which could leak and perhaps present coolant at the back of the motor and drip down over the bell housing.
For more discussion about the welch plugs, type in "alloytec welsh plugs" in the search box. The VZ V6 has a few threads about hard to find obscure leaks, and the welsh plug is mentioned many times. As are porous cylinder heads and their treatment.
I have not read anywhere, perhaps I missed it, but there seems to be no contributor who actually replaced them, the welsh plugs, and cured the problem. A few references are made that they are replaced by someone. Maybe they are more of a desperation replacement. My apology if I missed the submission. Would appreciate a link to the actual replacement by a member of this forum as it would help clarify if the alloytec block is fragile, porous etc in the valley area.
The best bet is to get an inspection mirror as suggested by contributor, alloytec sludge.
