Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages--Refer to Diagnostic Starting Point - Engine Cooling .

Coolant consumption may or may not cause the engine to overheat.

1. Inspect for spark plugs saturated by coolant. Refer to Spark Plug Inspection .
2. Perform a cylinder leak down test.
3. Inspect the cylinder heads and engine block for damage to the coolant passages and/or a faulty head gasket.
4. Repair or replace as required.