Manual:HUMMER Hummer H3 Base 2010Page:10131 / 37523



Coolant in Engine Oil — 2010 Hummer H3 Base, Automatic Service Manual

Coolant in Engine Oil

Cause Correction
DEFINITION: Foamy or discolored oil or an engine oil "overfill" condition may indicate coolant entering the engine crankcase. Low coolant levels, an inoperative cooling fan, or a faulty thermostat may lead to an "overtemperature" condition which may cause engine component damage. Contaminated engine oil and oil filter should be changed.
  • Inspect the oil for excessive foaming or an overfill condition. Oil diluted by coolant may not properly lubricate the crankshaft bearings and may lead to component damage. Refer to Lower Engine Noise, Regardless of Engine Speed .
  • Inspect by performing a Cylinder Leakage Test . During this test, excessive air bubbles within the cooling system may indicate a faulty gasket or damaged component.
  • Inspect by performing a cylinder compression test. Two cylinders "side-by-side" on the engine block with low compression may indicate a failed cylinder head gasket. Refer to Engine Compression Test .
Faulty external engine oil cooler Replace the components as required.
Faulty cylinder head gasket Replace the head gasket and components as required. Refer to Cylinder Head Cleaning and Inspection and Cylinder Head Replacement .
Warped cylinder head Replace the cylinder head gasket. Refer to Cylinder Head Replacement .
Cracked cylinder head Replace the cylinder head and gasket.
Cracked cylinder sleeve or engine block Replace the components as required.
Cylinder head, block, or manifold porosity Replace the components as required.
Faulty sealing on engine front cover Reseal or replace front cover.