Whistle sound from Valve Cover breather tube..Weird

[MyToy]

Greetings:

I replaced my AC Compressor and ran the van up. After about 3 minutes is starts to whistle, almost like it was a belt squeak. It kinda sounded like it was in sync with the engine speed. Checked all belts, pulleys, idlers, etc. There was no noise coming from any of them. However what I noticed was when I turn the engine off the whistle did not stop, instead it continued for about 1 sec then slowly went away.
So the next thing I did was get it to whistle again and open up the radiator cap, no change, then the oil cap, bang! it stopped. Then the PVC, no change, then the breather from the valve cover to the fuel manifold and it stopped. Then I plugged up the breather on both sides and it stopped. So by removing the manifold out of the picture it stopped, doesn't run as good but at least stopped.
Checked all around the manifold for noise and could not hear a thing. I just cannot locate where it is coming from.

Any ever have this issue?

MT

[Burntboot]

MT - Just wanted to say that its nice to know other people run into weird/strange/stupid things, just like me, almost makes me feel normal

I don't have a clue what's going on and am having trouble envisioning your process but ....

Whistling sounds have always ended up being vacuum leaks for me and a whistle that occurs after shut down then fades away, makes me want to look at all things vacuum. Brake booster, EGR, VSV's, dash pots...
Get it making the noise and use a stethoscope to listen to each device and you should be able to narrow it down the source

I've been chasing a suspected vacuum leak on Suzy for several years now, (recurrent lean code)
I wont bore you with all the details, only that it has inhaled large sums of money with no solutions.
It has a slightly lumpy idle, intermittent ac problems and throws intermittent lean codes.

Due to C19 I haven't been out much, fired it up yesterday after being parked for 2 months and it starts whistling like Dixie
It has never ever whistled before!
Pulled the hood release and spent the next 20 mins trying to get the hood open (latch and hinges all seized!)
By the time I got access the noise had stoped.
My point being, while I had convinced myself I had eliminated all potential vacuum leaks, I must have missed something.
Given that it passed all leak tests to date, I am contemplating the possibility off an internal leak, like a VSV that isnt fully closing....

[MyToy]

Hey good hearing from you.

I did not get a notice that you replied, I just looked up my post and there it was. Yeah!

OK, have done a lot more investigation on this.

The sound is more of a chirp. Almost sounds like a belt/pulley issue, but it is not. Tried the scope idea and just could not find it.
It happens after the car is warm. I loosen the oil cap and it goes away. I pull the breather pipe from the valve cover to the mix manifold and it stops but runs rough, of course. I pull the PCV off the manifold and nothing happens and continues to chirp.
So I talked to a buddy of mine and he ask me if I listened under the engine. Well, no I didn't. So I went under and sure enough the chirp is coming from inside the oil pan area. OH OH!

He said that our year of engine uses a closed PCV system to draw the crank ventilation and pressure into the mixture only to be burned when mix with air. This pressure is serious in that if it does not have a release it can do some serious roflroflroflrofl. The chirp, in his opinion, is the pressure being pushed out some where. He said to check for oil leaks. The pressure can be so great it will push the oil right through a seal. So I went back and put back all the hoses and started it. After warm up it started chirping again. I pulled the PCV out and it stop. So the PCV plunger may be not opening at idle where the suction is not as great. I am getting a new one today to stick in. It may solve it.

He do you happen to have a picture of where the PCV goes into the manifold? I am hoping the bozos that worked on the fuel injection put it back in the right port of the manifold.

I will let you know.

Good talking to you again BurnBoot!

MY