7.8L LG4 Diesel Engine - Oil Leak - kw WT55 MD FRR Duramax 6HK1-TC PCV crankcase breather corrugated vent tube restriction plug excessive pressure loss dipstick

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Some dealers have reported loss of oil from around the oil dipstick tube during extensive driving in extreme low ambient temperatures on 2003-04 Medium Duty models with the 7.8L (6HK1-TC) diesel engine. The oil loss is the result of ice build up in the PCV vent breather tube from moisture collecting and freezing along the corrugated baffle area at the end of the vent tube. The ice build up will restrict and /or plug the vent tube causing excessive back pressure in the engine which can push oil out the dipstick tube. Inspect the engine for evidence of oil residue around the oil dipstick tube area during cold weather operation.

Replace the original corrugated baffle vent tube with the following new open design PVC vent breather hose and attaching parts which will prevent moisture build up and icing during extreme low ambient temperatures.

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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. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

All 2003-2004 GMC, Chevrolet C/T 65-75-85 and Isuzu F 65-75-85 Medium Duty Truck Models Equipped with the 7.8L (6HK1-TC) Option GL4 Diesel Engine.

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