There are several things that can cause this.
Earlier model 7M engines have a rubber plug on a coolant line near the firewall on the exhaust side. It can fail under constant head cycles from the exhaust manifold, and when it does it will dump all your coolant. It's about $4 to replace and can save you a costly engine rebuild.
A faulty hose from the radiator neck to the overflow bottle will cause coolant to spill out but air to get pulled in. A few cycles of this will cause you car to start to overheat. Same problem with the pickup line in the overflow bottle.
Faulty thermostat will cause overheating.
Faulty radiator cap will cause coolant loss, then overheating.
The fact that our radiators are finer mesh than our intercoolers / ac condensers will allow gunk to pass through the first two but get stuck on the front of the radiator. This results in no airflow over the radiator, which again makes for overheating.
Worse, these make a BHG much more likely, as an overheated head will often warp enough to let the head gasket leak, at which point things rapidly get worse.
