Quirky little engine noise i cant quite pinpoint

[Fishinforchikin]

I got a 2004 xlt super cab 189k miles with the 3.0 and its got a little knocking noise. It only comes out when it’s fully warmed up. It is loudest at idle and when i let off the gas pedal. Also when i slightly apply the smallest amount of throttle. I put in new crankshaft and camshaft position sensors and upped the oil thickness to 5w30 but no luck. You can hear it from the hood, but its loudest under the truck and in through the right front passenger wheel well. I have tried the stethoscope but i don’t think im pinpointing the noise very well. It does get faster through rpms. So somethings definitely hitting something. Anything i can do to test exactly where the sound is coming from? The truck has had a new rear main seal put in.

 

[superj]

Anyone near by that can help pin point?

Maybe its the ac or alternator?

 

[Fishinforchikin]

Nah. Ac turned off the sound still goes. If anything, sometimes the blower makes its own funny noises haha. But usually quiet and functional. Alternator would have been ruled out by now. Right up in your face in the engine bay, i even tested that with the stethoscope. Just regular lightning n thunder noises. For sure it isnt rod knock, my truck would be toast by now. Maybe pushrods? Timing?

 

[alwaysFlOoReD]

Try taking the belts off temporarily. That should make it quiet enough to better pinpoint the noise.

 

[Fishinforchikin]

How would i go about doing that? What pulleys would not have the belt on them

 

[pjtoledo]

for a variation of the stethoscope try a hose.
you can tell the difference if it's pointing at, or away from the source.

idler pullies??

 

[alwaysFlOoReD]

How would i go about doing that? What pulleys would not have the belt on them

Make sure there is a diagram of the belt routing. There will be a tensioner pulley that has a square hole in the middle (typically). Use a breaker bar to move the tensioner to slacken the belt and pull it out. Fire up the engine and listen. If the noise is still there then you know its not anything driven by the belt. If it's still there it should be much easier to locate. Running the engine without a belt is fine for several minutes when starting from cold.

 

[Fishinforchikin]

Make sure there is a diagram of the belt routing. There will be a tensioner pulley that has a square hole in the middle (typically). Use a breaker bar to move the tensioner to slacken the belt and pull it out. Fire up the engine and listen. If the noise is still there then you know its not anything driven by the belt. If it's still there it should be much easier to locate. Running the engine without a belt is fine for several minutes when starting from cold.

Ah i see, this should work because there’s a separate chain for the cam and crank, so i can run it without a belt for a while. The thing is that the sound is only heard when the engine’s completely warm. My next oil change i want to go to 10w-30… just maybe it’ll do sumthin.