I work at a shop and we have recently gotten a customer with the complaint of a squeaky belt. Of course if you heard this noise you'd know it wasnt the belt, however we removed the belt anyway. Noise is still there.

The noise is a squeal that makes me grit my teeth. It sounded like a dry rocker fulcrum. We pulled the valve covers to find that there are no rocker fulcrums, however we did find that the pushrods were badly worn and they would no longer spin in the rocker. The top of them were severly grooved as opposed to polished as the lifter side was. I went to the boneyard and found a set of rockers, shafts, and pushrods. I cleaned and lubed everything but the noise was unchanged. The frequency is proportional to RPM but it doesnt get lounder. It is unaffected by engine load.

The noise is not constant. It comes and goes. The sound is like a ballbearing that is not rolling in its race, like it has a flat spot.(very hard to describe) I thought maybe a roller lifter may have a flat spot? Its such a strange noise because when we are ready to hear it with stethoscopes on a lift it wont makethe noise. The noise is not affected when its in gear or neutral. It sounds like its at the rear of the engine above or in the bellhousing, but I cant visualize anything in an engine that would make this noise.

We are stumped and i turn to you guys for any input or past experiances. I cant imagine a sporadically spinning cam bearing. But that would be in the general area. Let me know guys. Just start saying the first thing that comes to mind... OK not the first thing. You know what to do FTE!!!

 

Watch this youtube video: YouTube - WRX blown engine

If the squeak sounds like that, then you have blown main bearings.

 

We know what a blown engine and spun bearings sound like, I said we're stumped which means we don't know what the noise is. Its obviously NOT main bearings. The engine runs great. The squeak isn't constant, the customer's only complaint is that its annoying not severe. Oil pressure is within spec. It still sounds like a dry/worn rocker fulcrum (if you can visualize the sound and frequency. That subaru is a good example of spun bearings though.

 

Perhaps cracked or broken flex plate, or a failing torque converter. The flexplate on my neighbors 4.0 explorer cracked right off the hub.

 

Get that stethoscope and aim it close to the bottom of the coilpack, there is a bushing where the old style distributor used to sit, just a guess, but have had sqeeks eminating from that spot.. sound carries down the back of the bell housing.

 

Did the 4.0 ever have a distributor? I know the 3.0, 3.8, and 4.2 have the synchronizer is that what the 4.0 has too? If there is a bushing there I'd but my best buck on that being the source of the squeak. It sounds just like that type of noise. Thanks for the replies guys! I'll let you know how we make out with that truck.

 

I just checked all data and this engine does have a synchronizer. That has got to be it, it sounds like exactly where the noise is coming from. Thank you so much, I wasnt aware this engine had one. Alldata shows it under CMP sensor, and nowhere else. Thank you very much.

 

Well that makes sense! I forgot that the 4.0 OHV when to coil pack fired ignition. Ford seems to have trouble with engines that started out as distributor fired then converted to coil pack.