Crankshaft Rear Oil Seal Leaks During Extreme Cold Weather Operation (-29 Degrees C/-20 Degrees F) (Modify Oil Separator)

Some customers may comment on crankshaft rear oil seal leaks during extreme cold weather operation. Typically -29°C (-20°F) and below.

A restricted positive crankcase ventilation (PCV) system may be caused by frozen condensation, ice, or snow that has accumulated in the vent tube at the bottom of the generator bracket. In extreme cold weather, the vent tube may not be subjected to enough heat from the engine compartment to melt the ice or snow. Excessive crankcase pressure may develop and cause premature oil seal failures. While the oil leak may occur anywhere on the engine, the crankshaft rear oil seal is the most susceptible due to the larger surface area in which crankcase pressures can act upon. The excessive crankcase pressure may not be apparent in the shop as the vehicle warms up and the blockage in the vent tube thaws.

Create a secondary atmospheric vent path for the PCV oil separator housing using the following procedure. This location is protected from the elements and is not subject to freezing. A secondary atmospheric vent path was implemented to production in February of 2003.

1. Remove the generator bracket. Refer to Drive Belt Tensioner and Generator Mounting Bracket Replacement.
2. Remove the positive crankcase ventilation (PCV) oil separator cover bolts.
3. Remove the positive crankcase ventilation (PCV) oil separator cover and gasket.
4. Drill a 10 mm (25/64 in) hole (1) through the back of the generator bracket. The hole (1) should be located higher than the vent tube (2).
5. Clean any debris from the oil separator housing.
6. Install the positive crankcase ventilation (PCV) oil separator cover and a new gasket.
7. Install the positive crankcase ventilation (PCV) oil separator cover bolts.

Tighten
Tighten the positive crankcase ventilation (PCV) oil separator bolts to 8 N·m (71 in lb).

8. Install the generator bracket. Refer to Drive Belt Tensioner and Generator Mounting Bracket Replacement.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: