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Discussion Starter #1
I posted a 30-second recording of my engine compartment noise here:
http://www.prpcompany.com/noise.wma

In another thread at http://www.focusfanatics.com/forum/showthread.php?p=3752559#post3752559, I wondered about the possibility of this noise being connected to a couple other problems I have with my tranny and an uneven idle.

But for the moment I thought I'd just see if I could figure out the noise and then go from there.

From the passenger compartment, this noise sounded to me like a belt/pulley bearing sort of noise, but when I popped the hood I was surprised to find that the noise didn't seem to be coming from the belt side of the engine.

The noise doesn't change with rpm's, and it doesn't matter whether the car is in park or drive.

Anyone recognize this?
 

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Use a length of vacuum (rubber hose) to try to find where the noise is coming from? Don't use metal....keep hands away from moving parts, etc. One end near your ear...the other to find the source. Or go steal a plastic stethoscope from a Candy Striper (no...not a Candy Stripper [:)] )
 

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Discussion Starter #4
It turns out that the idle problem and the engine compartment noise (which I'll now describe as a sharp hiss, though it initially sounded to me like a light mechanical noise) were due to a problem with a PCV hose. The hose that runs from the PCV valve connects to the intake manifold via a molded rubber elbow. That elbow degrades over time, and initially it sucks closed (collapses on itself), and eventually develops open holes or cracks.

Now that I know what was going on, further searches on this forum and elsewhere show that it is a commonly reported problem.

One annoying development though: The hose is composed of 3 parts - a molded rubber elbow that connects to the PCV valve, a long center piece that is a plastic pipe with a foam sheath, and the molded rubber elbow that connects to the nipple on the intake manifold. I understand that Ford used to sell all 3 parts separately, and you could get that elbow for a few dollars. Now they only sell it as an assembly (P/N YS4Z-6758-A), and I paid $39 for it. I thought that it was because Ford had improved the trouble-prone elbow (as I understand they have for the Zetec engine -- mine is a 2002 SPI engine). But no, it appears to be the same molded rubber elbow, except that now it is available only as part of the expensive assembly.

Rock Auto, Advanced Auto, AutoZone and NAPA only have the PCV valve itself. Several of them offered to match my elbow to a universal elbow, but I have seen perhaps a couple posts where people did that and found that the replacement elbow was soon showing the same collapsing behavior. So I gritted my teeth and bought the Ford assembly.

But the car has 81,000 miles on it. If that elbow was the original and the replacement goes for another 80,000 miles, then it was an annoying "periodic maintenance" job that won't be faced again soon.
 
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