My 06 s40 has developed a strange whistling noise, video here:

Recently I replaced the overflow tank because it was cracked and leaking. The car idles really rough, and I don't know what it is. I don't think it's the PCV oil trap because it doesn't go away with the dipstick. What could it be?

 

Every time you removed the dipstick or oil fill cap the noise started! That is crazy. Have you tried removing both the dipstick and oil fill cap at the same time just to see what happens?

Given the Volvo's history with the oil trap I would have to start there. Just a guess.

 

I agree. Especially since it might be free.

 

I noticed a lot of yellowish sludge buildup was evident early in the video when the oil filler cap was removed the first time.

 

I have almost the same issue. I just replaced the timing belt.. check engine light is on. I believe is my alternator because all my lights on the dash board and the speedometer goes crazy. I get all kinds of warnings. I am driving and the speedometer goes down to zero. power steering lights is on, but I still have the stereo working and regular lights also. front and rear passenger doors wont unlock either....This is driving me crazy. Help!!

 

Does your PCV tube have cracks? There is a unlimited recall for this:

http://forums.swedespeed.com/showthread.php?108593-PCV-Recall/page3

They just did it for me @$0.00

 

Mods, Jenifer15 is a troll and is spamming this forum with links to who knows where. Please delete the account.