Dipstick Tube O-Ring Oil Leak

When diagnosing engine oil leaks on 2019-2022 Silverado, Sierra; and 2020-2022 CT4-V models equipped with the 2.7: turbocharged 4-cylinder engine (RPO L3B) (Fig. 22), inspect the dipstick tube (indicator tube) O-ring and areas above the composite oil pan sealing surface. These potential oil leak areas should be checked before determining the lower composite oil pan as the source of the engine oil leak. The oil leak may have a similar appearance to an engine oil cooler leak.


Fig. 22


Signs of oil spray may be seen on the left side of the engine or the oil leak may only occur after a road test on the left side of the engine.

Check for an oil leak from the dipstick tube O-ring with an inspection mirror. (Fig. 23) There may not be any oil residue around the dipstick tube O-ring area.


Fig. 23


Remove the dipstick tube and inspect the dipstick tube O-ring for damage. Replace as necessary. Use extra care when replacing the dipstick tube. There may be sharp edges on the lower crankcase extension that could potentially damage the O-ring during installation. (Fig. 24]


Fig. 24


Verify that the dipstick tube does not show any signs of damage or leaks to the seal before replacing the oil pan gasket. A black light and tracer dye can be used to identify an oil leak from the composite oil pan sealing surface. (Fig. 25)

TIP: The use of engine oil dye and trace powders are recommended to assist with isolating engine oil leak points. Be sure to clean suspected leak areas thoroughly before using trace powders.


Fig. 25


Lower Oil Pan

The composite oil pan is attached at the engine block lower structural extension (LCE). The oil pan incorporates four jack screws (threaded inserts) that need to be used during the removal procedure. (Fig. 26) Tighten the jack screw by hand 1 to 2 turns. Turn each uniformly and move to the next screw until the oil pan has full separation from the LCE. Do not pry on the oil pan to LCE or the sealing surface may be damaged.


Fig. 26


Refer to Bulletin #21-NA-231 for additional information.


– Thanks to Marcus Plant

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