Mysterious engine squeak (not a belt)

[dirttracker]

I have a 2002 with ~113,000 miles that has developed a mysterious squeak in the engine. It sounds like a belt chirp, but the noise remains when the engine is run with neither belt installed. It is not present during the first start of the day. It appears after a maximum of 5 minutes of operation. It seems to get a little worse after longer trips of 30 minutes or more. The chirp varies with engine speed and seems to disappear (or at leaset I can't hear it) over 2000 rpm. It's a hard noise to locate, but appears to be coming from an area between the center to the front of the engine. The noise is noticeably louder when listening through the oil fill tube using a short piece of hose. The noise does not affect performance (no check engine light, misfire, loss of mileage, etc). The noise will go away for 500 - 1000 miles after an oil change, after this it returns until the next oil change. I have owned the truck since it was new, it has had regular oil changes at no more than 5000 miles. I have never seen any debris in the engine oil. By my unscientific method of trying to count the noise using a stop watch, it appears to occur at 1/2 of the crankshaft RPM.

I have read these engines have roller rockers that have caused problems, does anyone think these may cause this kind of a squeak? I'm to the point where I need to start looking inside the engine for the cause of the noise and would like opinions on where to start. I have ignored the noise for some time, I thought it was a belt. Now that I know different I want to get it fixed before it becomes a real problem.

Sorry for the lengt of the post, I ahve tried to include everything I have observed. This noise has me and a couple of my profeesional mechanic friends baffled.

Thanks

Eric

 

[ygmn]

Could be hydraulic lifter leaking by...

 

[DougD]

Not to be insulting, but did you remove BOTH belts for this experiment?

 

[dirttracker]

Doug,

Both belts were removed.

I finally had some time to tear into it, it appears the #8 intake rocker arm is the source of the noise. I'll have new parts on Monday & replace all 16 rockers. Sure was a strange noise for a rocker arm. Hopefully all of the needle bearings are still in the rocker.

 

[Geovalanche]

Start counting. I believe there are 66 needles bearings per rocker arm (don't ask how I know that). If you want to try something to ensure nothing is wrong pull a magnet over the bottom of the oil pan toward the drain during an oil change. The pan is aluminum, so the magnetic field goes right through it.

 

[dirttracker]

Good idea on the magnet & thanks for the count on the needle bearings. I have a small one I was planning to go fishing with through the oil drain plug if I can't account for all of the needles. I've got a couple of really strong rare earth magnets I can try from outside the pan if needed.

Does anyone know if it is possible for one of the needles pass through the oil pump pickup screen? I'd imagine a needle sucked into the oil pump would not be pretty. On a couple of occasions I've left things I could not fish out in the oil pan (like a piece of pushrod) without any problems. As long as the debris makes it into the sump and is not small enough to pass through the pickup screen it should not cause problems.

 

[Geovalanche]

Good news; needles won't fit through the screen, too big. Cant' even really clog it easily due to the design of the pickup.

Getting a magnet through the oil drain hole is tough, but if you drag the magnet across the bottom you will pull out anything in there, such as needles.