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Q: Knocking when engine warms up

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My oil pressure is low. Additionally, after my truck warms up a knocking occurs, but while the engine is cold, there is no knocking.

A: When the engine is cold, the viscosity of t...

When the engine is cold, the viscosity of the oil is higher along with the internal bearing clearances in the engine. As the engine warms both the viscosity of the oil lowers and the engine bearing clearances can increase dropping oil pressure. Minimum engine oil pressure as a rule of thumb should be 10 psi for 1000 rpm the engine is running. To ensure this minimum pressure is maintained an engine oil pressure test should be conducted. If engine oil pressure is not maintained then an engine overhaul may be necessary. You may want to enlist the help of a mechanic, such as one from YourMechanic, who can run the oil pressure for you and suggest possible repairs.

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