2004 V70 non turbo with nearly 251,000 miles. Replaced the serp belt and timing belt along with the tensioner, idler and tensioner pulley in April 2021, but didn't replace the water pump at that time. Have driven 19,500 miles since then without any concerns until a couple weeks ago when I was 75 miles into a 180 mile trip to the dealer for air bag recall, made a pit stop and found my car had a high p[itched whistle coming from the right side. A quick search of the source of all knowledge (Google), got me to try pulling the dipstick. Dipstick out, no whistle. Dipstick in, whistle. Seems to be the PCV. Called the dealer, they would have to wait several days for parts and advised it would be better go home and take care of it there.
Ordered the all the stuff from PFC, it took about 2 weeks to get. This weekend the weather is cooperating, I do not have an indoor space to work in.
Just to double check i drove around a bit, got the engine all warmed up and tried the glove test.
My engine sucks. Big time. That glove just glued itself down.
The sound stops with acceleration, resumes in idle
No codes
Soooo, Do I assume its the PCV ?
Going to use a vehicle stethoscope to see if the whistle might be coming from some other part. I don't doubt that the PCV is due to be serviced but if we're going to tear into this it would make sense be sure it isn't something else causing this and take care of it in the process.
What should I be looking for?

 

My 2008 3.2 had high pitched whistle/squeal noise and replacing the oil trap fixed it.

Autopsy on the oil trap showed a ruptured spring loaded (likely vacuum regulator) rubber diaphragm. Your engine is obviously different but pulling the oil fill cap with the engine running made my noise go away.
New oil trap fixed the noise.

Thank you again ES6T for your help on that.

 

It is common on the later cars that have the pcv valve in the oil filter stand and the diaphragm breaks OR the 3.2 6cyl - for those to make that noise. But not yours.
The whistle/squeal is the sound of air being sucked past an oil seal - like the squealing noise of letting air slowly out of a balloon. The cause is the intake manifolde vacuum into the pcv system is not being controlled. On the turbo cars there is a fixed orifice - the banjo bolt on the bottom of the intake manifold that limits vacuum in the pcv system - not sure what part does that on a non - turbo car.
Looking at the parts page it appears that a 8631288 might regulate the amount of vacuum to the pcv system. Block off the hose (#16 if it goes to the oil trap) and see if it still squeals. Or see if vacuum is unrestricted thru that part

 

Will check these out.
Thank you!

 

There isn't a lot of info specific to the non turbos and Haynes is useless on this.

 

@Tinkerbell Sent you a PM

 

Replaced the oil trap PCV and have had no further problems with this.
Ordered the PCV Breather System Kit and an oil change kit (got the fancy Liqui Moly oil) from FCP Euro.

 

I appreciate the reply, I replaced my PCV today. Hopefully, it solves my issue as it did for you.