I am working on my friends car again and having a problem. This was the problem last time:
Here is some quick history: (it’* the L36)
Several months ago the FPR was leaking and caused a upper intake manifold failure (catastrophic), My friend took it to the local mechanic to replace the upper and some related parts. I have never trusted since he does a half-assed job most of the time, and sucks at trouble shooting. Anyway this time after several weeks there was a squeal that only happens at idle and only after a few minutes of idling.
And now the rest of the story:
The sound is from both the front and rear of the engine and is next to impossible to locate even with a stethoscope. I thought it was the idler and told Mauro to replace it. He did and still had the problem, it sounded as though the alternator bearings might be bad, and since he had a brand spanking new one we replaced it. After replacing it the sound “went away”. My bosses son bought the car and he was going to pick up the car but ha and Mauro heard a noise. I found I had screwed up and installed the belt one tooth off on the AC compressor (after telling my boss what a pain it was to make sure the belt was aligned on the crank pulley). This ruined the belt so I said if you get a new belt I will help him replace it. Yesterday they came in with the belt and we installed it (who came up with having to remove that stupid spacer ought to be flogged). All was well and he was set to drive it home, but after moving it out of the shop and around to the front as they were leaving it started squealing so it was parked. This morning my boss asked me to take a look at and see what I could find.
After starting it and about 3-4 minutes I started kicking it in and out of gear and turning on and off the AC it started making the noise again. I started poking around and could not locate the noise other than on either the crank ends of the engine seemed to emit this squeal. If you rev it up it goes away. I removed the belt and started it again within 10 seconds it came back and sounded like it was coming straight from the balancer (damper) area and still at the rear of the engine. Now I am thinking it’* a spun bearing except it goes away. Then I start to remove the engine cover with the engine running to see what I can figure out. I start to remove the oil cap and someone is pulling on it from the inside, the vacuum was tremendous. As I remove it air rushes in and the engine stumbles the squeal goes away and the engine recovers back to idle (stumble caused by unmetered air entering the system?).
The noise seems to be caused by air entering the front and (or) rear main seals, and is either a whistle or squealing because of the oil being drawn off the bearing surface at idle (when oil pressure is lower).
I cannot tell how the PCV system works, I am used to seeing a place on both valve covers, one for the PCV and the other for filtered air to enter the engine. It seems to me that the problem is the filtered air location is blocked causing this problem. My question is where and how is the system routed?