Common Issues and Failures of Core Plugs
The most common issue for core plug failure is an incorrect ratio or lack of antifreeze in the engine coolant. Either due to the vehicle being topped up with just water when it is showing low on the coolant tank or because the antifreeze is just old and needs replacing. It is vital the coolant is tested with an ethylene glycol tester at last once a year or even when the vehicle has regular service intervals.
Lack of antifreeze in the coolant will cause the core plugs to rust and rot out from the inside of the engine.
Another related issue to lack of antifreeze in the coolant more so in winter time is the coolant completely freezing, expanding and popping the core plugs. Most often than not causing water pump failure as well. In severe cases, it will ever crack the block or cylinder head.