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:
1. Improper oil viscosity.
^ Install proper oil viscosity for expected temperatures.
2. 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.
3. Excessive crankshaft end clearance; Replace the crankshaft thrust bearing.
4. Excessive front main bearing clearance; Replace the worn parts.
5. Timing chain tensioner malfunction; Clean, inspect and replace the timing chain tensioner, if required.