4.9 engine knock.

[adallak]

I have had this knock for nearly five years and thought it was the known #1 bearing problem since it shows up at cold start and disappears in a few minutes when the engine warms up. It comes back when the engine operates at temperatures higher than 180, but one can hear the “hot” knock only under load (unlike the cold knock which is quite loud at idle as well).

Since I was sure it was #1 bearing I changed the oil and Rotella 15-40 was supposed to take care of it. But nothing has changed. This morning I started the car with the serpentine belt off and the knock was there as usual. It seems to be located in the front of the engine.

What else could cause this knock? I hope this is not a serious issue … at least nothing happened in five years. Nevertheless, I would like to know what you guys think might be the problem.

Thank you!