Engine Knock Diagnosis. Cadillac Concours 1996

For 1990-2009 cars

### 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 Only 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 SECTION 0B.

• | Hydraulic lifter bleed down

- | Clean, test and replace hydraulic lifter, as necessary.

- | When the engine is off, some valves will open. Spring pressure against the lifters will tend to bleed the lifter down. Repair the lifter only if the problem is consistent.

- | Engines 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 the crankshaft thrust bearing.

• | Excessive front main bearing clearance; Replace the worn parts.

• | Timing chain tensioner malfunction; Clean, inspect and replace the timing chain tensioner, if required.

### 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. Refer to SECTION 0B for engine oil specifications.

• | 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. Install the correct piston.