Smartin,

Usually this type of leak is caused by the heater core or one of the connections going to it leaking. This won't affect the engine temperature until it leaks enough to lower the coolant temperature.

You might try putting a leak stop chemical in the radiator.

Also try running with the pressure cap loose to see if the leak stops.

Removing the heater core is a difficult but not impossible job but is very expensive because of the many hours involved unless you do it yourself.

P E H