Engine noise question

[chuck500cc]

On some days my M35 engine sounds like it is about to come apart and on others is as quiet as a gas motor. What gives? It burns no oil and is fresh, fuel filters are new, running better that 50% WMO and deisel mix, does not have any unusual "knock's" in the motor on cold start, oil preasure good at idle and at speed. But when setting at red lights, at temp, the motor sounds like it has a bag of marbles in it at times and others is very quiet.

Chuck XD Fan

 

[doghead]

Are you wearing ear protection? If not, try ear plugs, mine is nice and quiet with them.