I have gained a rattle type noise during idle. When you increase the rpm's it appears to stop or at least nearly stop. The sound is coming from the front of the engine. Has anyone ever heard of a fan clutch ratteling? How should I go about finding this culpret?
Thanks!

 

Does the noise change at low engine temp? High temp?

Fan clutch noise can also be confused with a bad water pump. The clutch bolts on to the water pump flange on this engine. Try disconnecting the belt and wobbling the fan. If it moves perpendicular to the crank shaft, I would suspect the water pump. Also spin it and listen for any grinding from the water pump brearing.

It is recommended to replace the fan clutch and water pump at the same time, but I've done the water pump job without a new fan clutch when my budget required it.

Also check the water pump weep hole. When the internal pump bearing goes, it usually weeps coolant from the hole.

Finally, I had an idle pulley bearing go out on me on another vehicle years ago. Not saying yours is bad, but mine started making noise. I kept looking for the culprit, but never suspected the idle pulley. It finally failed on me a few months later while accelerating on the highway. It should be easy enough to check with the belt disconnected. Grab the pulley and wobble it, checking for any play. If there is play or grinding noise/feeling when spinning it, I'd replace the pulley.

Just a few thoughts. Good luck!

 

Unfortunately I have found that my problem is in the motor itself. I removed the serpentine belt and started it up. With no pullys, fan, or the water pump turning, the noise is still there. I got under the truck and believe the noise is coming from the passenger side toward the rear of the engine. I used a rod against the ear method and still could not trace the location of the noise. About that time it started raining. Gonna have to wait for another day... Anyone with any other ideas I would love to hear them.
Thanks,
Chuck

 

Check the engine lifting bracket - it's what you hook the chain to when you pull the motor.

 

I hate to sound like a dummy but it has been a few years since I pulled the motor. Where is that lug at? Is it on the back of the motor? I tried looking with a flashlight but I couldn't see it..

 

Hmm - the 4.6 may not have them installed - on the 4.2 this is a common source of rattling if the fasteners loosen.

Another common source of rattling is the catalytic converter heat shields.

 

Well, well, well... I believe the noise is the timing chain. Using a stethascope the noise is loudest on the front of the passenger side timing chain cover. While I am in there I will go back with a new water pump. What my question is.... Would I have to unbolt motor mounts and jack up the engine to change the oil pump? Roughly 200,000 miles on the pump that is in there. What do you guys think?
Thanks,
Chuck