Engine Knocking

Noises in engines are sometimes characteristic of the design. Compare the sounds in other engines to make sure you are not trying to correct a normal condition.

KNOCKS COLD AND CONTINUES FOR TWO TO THREE MINUTES
INCREASES WITH TORQUE
- Flywheel contacting splash shield. Reposition splash shield.
- Loose or broken balancer or drive pulleys. Tighten or replace as necessary.
- Excessive piston to bore clearance. Replace piston.

Cold engine piston knock usually disappears when the cylinder is grounded out. Cold engine piston knock which disappears in 1.5 minutes should be considered acceptable.
- Bent connecting rod.

HEAVY KNOCK HOT 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.
- Exhaust system grounded. Reposition 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 Electronic Spark Timing.
- Loose torque converter bolts.
- Exhaust leak at manifold. Tighten bolts and/or replace gasket.
- Excessive rod bearing clearance. Replace bearings as necessary.

KNOCKS ON INITIAL START-UP BUT ONLY LASTS A FEW SECONDS
- Drain back from engine block. Install oil filter with internal check valve.
- Improper oil viscosity. Install proper oil viscosity for expected temperatures. Refer to Engine Lubrication. Engine Lubrication
- Hydraulic lifter bleed down. Clean, test and replace as necessary.
When the engine is stopped, some valves will be open. Spring pressure against lifters will tend to bleed lifter down. Attempts to repair should be made only if the problem is consistent.
- An engine that is operated for only short periods between start-ups may have lifter noise that lasts for a few minutes. This is a normal condition.
- Excessive crankshaft end clearance. Replace crankshaft thrust bearing.
- Excessive front main bearing clearance. Replace worn parts.
- Timing chain tensioner malfunction. Clean, inspect and replace if required.
A burst of timing chain rattle may occur after an overnight or 1-2 hour "Hot Soak". This is a NORMAL condition. This is caused by a 1-2 second delay in engine oil pressure build-up to the hydraulic timing chain tensioner.
- Oil flow check valve (head to block) missing or faulty.

KNOCKS AT IDLE HOT
- Loose or worn drive belts. Tension and/or replace as necessary.
- A/C Compressor or generator bearing. Replace as necessary.
- Valve train. Replace parts as necessary.
- Improper oil viscosity. Install proper viscosity oil for expected temperature. Refer to Engine Lubrication. Engine Lubrication

- Excessive piston pin clearance. Replace piston and pin.
- Camshaft drive gear backlash excessive. Knock will also be heard on a cold engine.
- Connecting rod alignment. Check and replace rods as necessary.
- Loose crankshaft balancer. Torque and/or replace worn parts.
- Piston pin offset to wrong side. Install correct piston.
- Timing chain housing idler sprocket bearing worn. Replace sprocket.