My 2002 Ford E-350 15-passenger van now makes a strange howling noise. The noise is especially noticeable when idling or at slow speeds. There has been no effect to performance other than this peculiar noise. The last three mechanics I've taken it to have had various theories, but no solutions other than the following advice, "Since it doesn't seem like a safety issue, drive it til it breaks." My van has 130,000 miles on it. It was fine before, but the problem started right after the 120,000 mile servicing. One theory was it was the catalytic converter starting to go, but the latest mechanic said no way since the check engine light would be illuminated - which it is not. Another theory was the wrong type of oil may have been put in at the last change. We changed it, but no, the howling continues. Still another theory was it was the PCV valve which was supposed to be replaced at 120,000 miles. We replaced it, but again no, Caspar is still with us. I have not taken it to a Ford dealer, since the van is out of warranty, but the last mechanic called a buddy at a local dealer, he said he’d never heard of such a problem. I've been told by a Ford dealer that there are no recalls on this model.
Help!

 

I'm no mechanic and obviosly can't hear the howl but I would consider the automatic. Check the oil level, smell the oil to see if burned and maybe change the oil. Waiting for it to break, don't seem to be a good idea. If not dangerous at least an expensive proposition.

 

What engine?

Try unplugging the IAC while it's howling.. Idle Air Control...