Our '10 volvo was making a high pitched whistle. The Volvo dealer replaced the oil trap. It seemed to solve the problem short while later, maybe aonth or so I noticed a noise again. Not as bad as before but none the less a honking like noise. I took it back to the dealer. They said the replacement trap must be defective. They replaced the trap. Now another 6-8 weeks later. Same noise returned. Car was in for oil change. While there shop indicated oil leak from front timing cover.
We bought this vehicle new. It has had the oil changed routinely every 4000 miles. All service is done on interval, 7500, ,15,30,60, etc. The vehicle has 160k now. Anything idenfied by the dealer as needing done throughout ownership has been done. Question is this: what else could be causing the PVC system problems and noise besides oil trap and what isn't the shop properly diagnosing?