Whether or not damage was done depends on how low the coolant really got. If the head was run completely dry, then damage is possible.

To refill and bleed, fill the overflow tank all the way to the top and run the engine. The system will bleed itself out. Keep on topping off the tank till it is ready to overflow, and when it won't take anymore, set the proper level of coolant.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record