Truck Repair: Coolant leak on GMC Sonoma - 2.2l, gmc sonoma, makeup mirror

Question
I have developed a coolant leak at the back of the engine on my 1994 GMC Sonoma, 2.2L - 4cyl, 108K miles.  There are no hoses in this area and I can see the freeze plugs and they are not leaking.  The leak appears to be at the back of the block, but I cannot get between the firewall and the block to locate the leak.  Any thoughts ?
Thanks!
Jim

Answer
Hi Jim,
The heater core could be leaking, and draining out the a/c condensation drain.
If it seems to be coming off the engine, then intake manifold or head gasket would be my thought.
Some tricks to seeing back there are to get a mirror, like a makeup mirror that isn't tinted, and a light, and have the vehicle in a dark shop, or do it at night, so the sunlight doesn't hinder your vision in the mirror.
Don't use one of those yellow plastic droplights, cause they tend to blind you as much as light up the work.
Might also look up in there from below if you haven't.
If the heater core is leaking, you should smell it when you are driving, or have the defroster on.

Van