GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Malibu 🢒 Engine 🢒 Engine Mechanical - 2.4L 🢒 Engine Noise Diagnosis

Checks

Action

Intermittent Noise on Idle, Disappearing When Engine Speed is Increased
    • Dirt in the lifter. Replace the valve lifter if necessary.
    • A pitted or damaged valve lifter check ball. Replace the valve lifter if necessary.

Noise at Slow Idle or With Hot Oil; Quiet at Higher Engine Speeds or With Cold Oil

High valve lifter leak down rate may cause noise at slow idle or with hot oil. Replace the valve lifter.

Noise at High Vehicle Speeds, Quiet at Low Speeds

Noise at high vehicle speeds may be caused by the following conditions:

    • High oil level. Oil levels above the FULL mark allows the crankshaft counterweights to churn the oil into foam. When foam is pumped into the valve lifters, they will become noisy since a solid column of is required for proper operation. Drain the oil to the proper level.
    • A low oil level. Oil below the ADD mark allows the oil pump to pump air at high speeds, which results in noisy valve lifters. Add oil as necessary.

Noise Regardless of Engine Speed

Excessive valve lash may cause engine noise.

  1. Excessive valve lash may be caused by the following conditions:
    2. • A worn valve stem tip or lifter plunger. Replace the valve and the lifter.
    • Improper lubrication of the lifter. Replace the lifter and the camshaft .
  2. Check the lubrication system feed to the lifter.
    3. • If the valve and lifter plunger are OK, trouble in the valve lifter is indicated. Replace the valve lifter.
    • Check the oil feed passages to the lifter for dirt and debris.

Valve Train Noise

The following conditions may cause valve train noise:

    • Low oil pressure.
    • Broken valve spring.
    • Sticking valves. Inspect the valves.
    • Worn, dirty or faulty valve lifters.
    • Worn or faulty camshaft. Replace the camshaft.
    • Worn valve guides. Repair as necessary.

Vibrating or Rattling from Exhaust System

Vibration or ratting from the exhaust system may be caused by loose and/or misaligned exhaust components. Align, then tighten the connections. Check for damaged hangers or mounting brackets and clamps.

Exhaust Leakage and/or Noise

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

    • Leakage at the exhaust component joints and couplings. Tighten the clamps or couplings to the specified torque.
    • Improper installation or misalignment of the exhaust system. Align, then tighten the exhaust clamps.
    • A cracked or broken exhaust manifold. Replace the exhaust manifold.
    • A leak between the exhaust manifold or the cylinder head. Tighten the exhaust manifold to the cylinder head nuts and bolts to specifications.
    • A damaged or worn exhaust seals or packing. Replace as necessary.
    • A burned or rusted out exhaust pipe. Replace the exhaust pipe as necessary.
    • A burned or blown out muffler. Replace the muffler assembly.
    • A broken or loose exhaust clamp and/or bracket. Replace as necessary.

Knocks Cold and Continues for 2 to 3 Minutes
    • 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.

Heavy Knock with Torque Applied
    • Broken balancer or pulley hub. Replace parts as necessary.
    • Loose torque converter bolts.
    • Accessory belts too tight or nicked. Replace and or tension to specifications as necessary.
    • Flywheel cracked.
    • Excessive main bearing clearance. Replace as necessary.
    • Excessive rod bearing clearance. Replace as necessary.

Light Knock Hot
    • Detonation or spark knock. Check operation of EST or ESC. Refer to Engine Controls.
    • Loose torque converter bolts.
    • Exhaust leak at the manifold. Tighten the bolts and/or replace the gasket.
    • Excessive rod bearing clearance. Replace bearings as necessary.

Knocks on Start-Up but Lasts a Few Seconds

The following conditions may produce engine knocks on initial start-up, but only last a few seconds:

    • Improper oil viscosity.
    • Install proper oil viscosity for expected temperatures. Refer to Maintenance and Lubrication.

Knocks at Idle Hot
    • Inspect the drive belt for wear. Check the tension and/or replace as necessary.
    • Inspect the A/C compressor or generator bearing. Replace or repair as necessary.
    • Inspect the valve train. Replace the parts as necessary.
    • Inspect for improper oil viscosity. Install proper viscosity oil for expected temperature.
    • Inspect for excessive piston pin clearance. Replace the piston and pin as necessary.
    • Inspect the connecting rod alignment. Check and replace the rods as necessary.
    • Inspect for insufficient piston to bore clearance.
    • Hone the bore and fit the new piston.
    • Inspect the crankshaft balancer for looseness. Torque and/or replace the worn parts.
    • Ensure that the piston pin is not offset to the wrong side, or that the piston is not installed backwards. Remove and replace the piston or reinstall it properly.