The coolant is leaking into the head gasket.
Hi, some of these engine cylinder heads were manufactured with a machining flaw that will leak coolant on the right side of the cylinder head. A coolant pressure test of the head will need to be done to verify the leaking head. If the leak is present then a new cylinder head will be needed to fix the problem. The vehicle date code of 9/99 to 10/99 were the listed as ones to have the flaw.
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