Welcome back:
I would wait until the temperature drops enough to make a difference. As far as rust and the bolts being tight, that usually isn't normally the cause of the leak but rather the gasket itself, the manifold warps from heat, or a crack in the manifold itself.
You may be 100% correct. It could be in the engine. However, this is a good engine and with only 73,000 on it, there really shouldn't be engine problems, but anything is possible.
See if there is a change when the temperature drops.
Let me know.
Joe
Wednesday, February 6th, 2019 AT 8:07 PM