Engine Noise Diagnosis

There are four steps to diagnosing engine noise. You must
determine the following conditions:
- Type of noise.
- Determine the exact operating condition under which the noise exists.
- At what rate, and at what location in the engine.
- Compare sounds in other engines to make sure you are not trying to correct a normal condition.

Identify the type of noise. For example, a light rattle or low rumble.
Remember, engine noises are generally synchronized to either engine speed (caused by the crankshaft, connecting rods or pistons) or one-half engine speed (valve train noise). Try to determine the rate at which the noise is occurring.
- Engine flywheel contacting the splash shield. Reposition the splash shield.
- Loose or broken crankshaft balancer or drive pulleys. Tighten or replace as necessary.
- Excessive piston to bore clearance. Replace the piston.
- Cold engine knock usually disappears when the specific cylinder secondary ignition circuit is grounded out. Cold engine piston knock which disappears in 1.5 minutes should be considered acceptable.
- Bent connecting rod
- Improper oil viscosity
- Install recommended oil viscosity for expected temperatures
- Excessive piston to bore clearance
- Excessive piston pin to piston clearance
- Excessive crankshaft end clearance
- Excessive crankshaft bearing clearance
- Detonation or spark knock
- Check operation of ignition controls or knock sensor circuit
- Loose torque converter bolts
- Exhaust leak at manifold
- Tighten the exhaust manifold bolts and/or replace the gasket.
- Excessive connecting rod bearing clearance. Replace bearings as necessary.
- Excessive piston pin clearance.
- Excessive crankshaft thrust bearing clearance.
- Bent connecting rod.