6.5L Diesel Cylinder Head Cracks Between the Valve Seats - kw L56 L57 L65 diesel leak coolant

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Surface cracks may be found between the valve seats on the 6.5L diesel engine cylinder head.

It is an inherent charateristic for some surface cracking to occur between the intake and exhaust valve seats on the 6.5L diesel engine. There are several factors which relate to the cracking including the use of induction hardened seats (the seat is an intergral part of the casting), temperature range, rate of expansion and contraction in the valve seat area, and the type of vehicle use. It is feasible these cracks can eventually form on every 6.5L diesel engine. The point at which this occurs in the life of the vehicle is directly effected by factors including vehicle use, horsepower, torque output of the engine, and the temperature of operation.

No repairs are recommended for the cracks between the valve seats. There have not been any verfiable instances in which these surface cracks have caused engine damage or coolant loss. This PI does not address the cracking in the cylinder head pre-chamber inserts. Cylinder head pre-chamber inserts are replaceable. Pre-chambers only need to be replaced if there is a crack which exceeds 3/16 of an inch or 5 mm in length. Cracks in the pre-chamber inserts shorter then 3/16 of an inch do not need to be addressed.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

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