[Tom Wells]

Mike,

Exactly - the hole in the thermostat flange is to assist burping. If mine has air in the cooling system, it overheats. If it gets burped over 3-5 heat/cool cycles it is fine.

I have a catch can attached to the radiator overflow.

When the engine is hot, the water expands, driving some of the air out through the tube. The air comes out because the overflow is attached nearly at the top of the radiator where the air can accumulate.

As the engine cools, water is sucked back in from the overflow can, so it is vital to keep its water level above the end of the tube.

Tom