Engine Noise Diagnosis. Holden Commodore Executive 2005

GM Service Manual Online

For 1990-2009 cars only

Makes 🢒 Holden 🢒 2005 🢒 Commodore Executive 🢒 Engine 🢒 Engine Mechanical - 5.7L (LS1 Export) 🢒 Engine Noise Diagnosis

There are four steps to diagnosing engine noise that must be determined:

The type of noise--Determine if the noise a light rattle/tapping or a low rumble/knocking noise.
The exact operating condition under which the noise exists--Factors such as the ambient temperature, the amount of engine warm-up time, the engine temperature, engine speed and load and other specifics.
At what rate the noise occurs, and at what location in the engine--Remember, engine noises are generally synchronized to either engine speed (crankshaft, flywheel, connecting rods, balancer, or pistons and related components) or one-half engine speed (valve train noise such as rocker arms, valve lifters, and timing chain) Try to determine the rate at which the noise is occurring. Use a timing light to assist in determining the knock speed. Two knocks per flash is crankshaft speed and one knock per flash is camshaft speed.
Compare the engine sounds to other engines--If possible compare the engine noise to another engine as this will verify that you are not trying to correct a normal condition.

Checks

Actions

Noise on start-up but only lasts a few seconds

This noise condition may be caused by:

•	Incorrect oil viscosity--Change the engine oil with the recommended oil viscosity for the expected temperatures.

•	Incorrect oil filter without the anti-drain back feature

•	Worn or dirty hydraulic valve lifters

•	Excessive piston to bore clearance

•	Excessive piston pin to piston clearance

•	Excessive crankshaft bearing clearance

Knocks when cold and continues for 1 to 2 minutes

Important: A cold engine knock usually disappears when the specific cylinder's secondary ignition circuit is isolated.

Common causes for a cold start knock are:

•	Loose or broken crankshaft balancer or accessory drive components

•	Excessive piston to bore clearance

•	Cracked piston

Intermittent noise on idle disappearing when the engine speed is increased

Intermittent noises at idle can be caused by:

•	Incorrect oil viscosity--Change the engine oil with the recommended oil viscosity for the expected temperatures.

•	Lower than specified oil pressure--Install an oil pressure gauge and measure the engine oil pressure.

•	Dirty or worn hydraulic valve lifter

Valve train noise (rattle/tapping)

The following conditions may cause valve train noise:

•	Lower than specified oil pressure

•	Worn or faulty oil pump

•	Loose oil pump to cylinder block bolts

•	Loose or damaged oil transfer tube and/or gaskets

•	Loose valve rocker arm attaching bolt

•	Worn valve rocker arm bearings

•	Worn valve rocker arm and/or pushrod

•	Broken valve spring

•	Sticking valves

•	Worn, dirty, or faulty hydraulic valve lifters

•	Worn hydraulic valve lifter guides

•	Worn camshaft lifter lobes

•	Worn valve guides or valve stems

•	Bent, broken, or damaged timing chain sprocket teeth

Knock at idle when hot (rumble/knocking)

The following conditions may cause a knocking noise:

•	Malfunctioning accessory drive system components

•	Loose or broken crankshaft balancer

•	Detonation (Pinging)--Check for correct operation of the cooling, knock, and ignition components. Refer to diagnostic information in Section 6C3-2 Powertrain Management -- GEN III V8 Diagnostics.

•	Excess piston pin to bore clearance

•	Bent connecting rod

•	Excessive connecting rod bearing, crankshaft main or thrust bearing clearance

•	Loose torque converter and/or flywheel bolts

•	Cracked or damaged flywheel or flexplate

•	Exhaust leak at the manifold

Exhaust system noise and/or leakage

Exhaust system noise and/or leakage may be caused by the following conditions:

•	Incorrectly installed or misaligned exhaust system components

•	Cracked or broken exhaust system manifold

•	Damaged or worn gaskets

•	Burnt or corroded exhaust components

•	A broken or loose exhaust clamp and/or bracket