By all indications the head gasket appears to be bad. The rear of the block and undercarriage is covered with oil. Service records from the dealer indicate that the head gasket needed replacement, and this dates back around 5 years ago. Anyway you put it the head gasket is going to eventually need replacement. I'm going to do the guides and seals while the head is off. Water pump has already been replaced in the last several years at the dealer, however, the car is filled with green coolant. Is this any reason for concern? I understand that you need only use the MB Coolant, but what are the exact reasons for this? Will the green coolant cause excessive harm to the engine and cooling system?