I have a 2002 z71 with 5.3, 200k miles. After about 10 min on the highways (65mph) I get what sounds like a rod knock. Twice, I stopped off to see what is going on. The knock seems to be coming from both sides or perhaps the middle front of the motor and quite pronounced. One time it went away just idling about a minute after I turned ON the AC (doubt that is related). In a few instances, after noticing the knock ~10 min later it was gone (basically when I get to work -- all highway: 65/75mph). It is hard to notice unless parked or driving close a K wall on the highway because there is a dumb Flowmaster installed. My father about two weeks prior to this thought it was an exhaust leak so I performed a smoke test with no leaks and forgot about it until I started driving the truck more regularly.

I have not had a chance to perform a ear-screwdriver-test. I have had this truck for almost 2 years. Oil pressure never gets above 40 (which is on the low end from what I read on forums). The fact that this happens only at operating temp then goes away is really confusing me. Thoughts?

Also, I am all set to do the timing chain gasket (and chain—already did the intake, knock sensors, valve covers and thermostat) the oil pump is a little pricey but might as well? Maybe engine flush first? Which makes me wonder if the knock could somehow be the chain… I know that might seem crazy…. I dunno…

 

Check for codes even if the CEL isn’t lit.

Standard rule for oil pressure on any engine is 10 PSI per 1000 RPM.

See if the noise gets louder by momentarily removing the oil fill cap.