I am trying to figure out this coolant leak. If I fill the expansion tank a bit too much I get a leak from what looks like my water pump or maybe from the front engine cover somewhere. It's hard to tell bit it's not from the head gaskets. The leak will then just stop when the coolant level get down a little below the fill line. But it also stops if I turn the heater on (I'm guessing this powers the pressure in the system).

I'm going to replace the water pump and gasket but was wondering if the water pump has a weep hole that could cause this?

Also is it possible for there to be a coolant leak front the gasket around the front engine cover (the part the water pump attaches to)? I'm just kind of at a loss where this leak is, it looks like it is dripping from the front left corner of the oil sump gasket (it's not but that is where the coolant runs to).

 

Yes the water pump has a weep hole, no it wont do this, if it were the weep hole it would trickle down the front of the water pump.
Yes the front engine cover gasket can leak coolant.

 

OK I'm thinking I am narrowing it down here, I am taking it to get pressure tested tomorrow and to see if the garage has any ideas.