Okay, I was driving home when all of a sudden my engine started "whistling." It sounded somewhere between a bearing on a the serpentine belt pulley, the belt slipping, or a vacuum leak. I could not figure out where it was coming from but it seemed to go away when I pressed on the fuel rail. I also noticed a small oil leak on the passenger side of the engine when I popped the hood which I had not seen before.

I searched and found all kinds of theories about how to fix the problem before running across one that actually helped. The good news is, this falls under the federal emission systems extended warranty so I am going tomorrow to get it fixed for free at the dealer. If only I had known before wasting all the time and effort replacing injector gaskets, cleaning injectors, cleaning the MAF sensor, cleaning the throttle body, etc.

The problem is in the crankcase ventilation system. The pressure builds up and causes the whistle as it is releasing the pressure. The way to diagnose it is simple. With the engine running, pull your dipstick. If you hear the pressure escaping, and the whistling goes away, that is your problem.

I hope this helps save somebody a lot of time and frustration. I have been dealing with this for weeks now! BTW, the service manager knew exactly what I was talking about as soon as I started explaining it. Apparently this is common. I cannot believe something so common was so hard to get an answer to, and the other solutions were expensive and time consuming, even for a DIY'er. Props to the guy who posted this and saved me. I cannot find the link again or I would give better props.

 

Great heads up. When you find out, if you don't know already, would you please let us know specifically what the solution is to this issue? I don't know what year S40 you're dealing with thus I'm not sure if it'd apply to my '01. It'd be nice to have that in my back pocket in case it comes up in the future. Thanks alot.

 

Note from dealer upon completion of work...
Fault traced to ECM250A Breather Box pulling too much vacuum on crankcase causing whistling noise. Replaced Breather Box.
FP-number 31338684-9 Description Oil Filter Housing

Service Manage described it pretty well saying it sounded like the Jetsons car.

 

the 2006 newer models exhibit the whistle when the system is restricted. VERY VERY common on those engines. The ones with the oil filter housing made onto the flame trap box are the only ones that produce the whistle.

I got to tell ya. PITA replacing the system on those. The plastic is so fragile, and the hardest part probably is getting the air filter assembly out of your way.

 

Sounds like a good topic for a step by step tutorial!?!? I am guessing I will need to do this again in 60k miles if I can't sell the car.