Faulty cylinder head gasket and/or cracking or other damage to the cylinder
head and engine block cooling system passages. 
Coolant consumption may or may not cause the engine to overheat. 
 | 
|     •  | Inspect for spark plugs saturated by coolant. |  
  
|     •  | Perform a cylinder leak down test.  |  
  
|     •  | Inspect the cylinder head and engine block for damage to the coolant passages
and/or a faulty head gasket.  |  
  
|     •  | Repair or replace as required. |  
  
 |