so ive been listening to this slight noise my engine has developed for just over a month now. came from the bottom end but i couldnt pinpoint it. today i took a long cardboard roll (thing gift wrap paper comes on) and i listened to the oilpan with it. it sounds like a "clackity" noise if that makes any sense. its louder when the engine has cooled off, as it warms up it gets quieter. can this only mean worn rod bearings? some days u can barely hear it some days its pretty loud. even when it is at its loudest however, if you rev the engine the engine noise drowns out the noise from the bottom end. whatever it is, its not affecting performance.

just as a note, i first started hearing it when i changed my oil. ive used mobil 1 10w30 the last two oil changes with no problem. my last oil change i used valvoline synthetic 10w30. is it possible that it is somehow related?

 

i doubt your oil change or oil type has anything to do with it, but maybe for the hell of it switch back to M1 and see what happens. it would be natural to be able to hear noise from the oil pan if you listened to it. as a rule with any sort of engine speed related noise i'd look for exhaust leaks and the injectors.

 

sometimes it is loud enough to hear just from being near the front of the car. if u stick your head near the wheel well its clearly heard. my question is what is the noise exactly? worn rod bearings? im just trying to gauge how serious of a problem it is and how long it may be before it starts to affect engine performance and driveability. or is it just going to drop a rod at random one of these days?

i thought bad rod bearings would get louder and louder with rpm? if u barely nudge the throttle u can hear the noise pickup speed but around 2300rpm u just cant hear the noise anymore over the engine.

 

I dont think its rod knock. Youd be able to hear that easily from the pass. compartment as a low reapeating metallic sound. My 350 does teh same thing. When its idling in P/N it makes a light 'clackity' sound thats heard through the oil pan and less from the top of the motor. Ive always attributed it to the cheesy lifters i stuck in with my cam. Ive never seen any metal in the oil or the filter so im not quite worried about it yet. Do you hear the noise from the top of the engine around the valve covers as well? If so it could jsut be the lash, especially if you dont use an oil filter with an anti drain back valve. With this cold weather the valves will be noisy for a minute or so untill they pump back up.

 

i cant really hear it from the top at all. definetely bottom end. someone suggested maybe a cracked flexplate?

 

With the motor running, start pulling plug wires on one cyl at a time. If the noise goes away it's either a rod bearing or wrist pin.. by not fireing that cyl, it will lower the presssure in it and not knock (usualy).

 

pulling plugs has no effect.

 

any other ideas? when i get a chance im going to take the bellhousing inspection cover off and see if i can find anything there. when the engine is cold and you first start it up you dont hear any signs of the noise. it always comes as its warming up and always goes away when cold.