Stock 2013 Cruze 1.4 Auto
102,500 miles
Past few months I've been hearing a squeaking coming from under the hood of my car. At first I thought it was the serpentine belt, so I replaced it with no luck. Then I thought it was the serpentine belt tensioner, so I replaced that with no such luck.
While looking about the engine while it was running and squeaking, I noticed that if I removed the oil dipstick or fill cap, the squeak would cease completely, but the engine would stumble and idle really rough but then recover somewhat. There's also a vacuum when I remove the dipstick and oil fill cap, whereby if I loosen the oil fill cap but still leave it on the valve cover, there's noticeable resistance to remove it from the suction. Also, the engine only really makes the squeak when it's up to temperature and I've been driving from some time.
While searching the forum, I came across the PCV valve issue threads so I've since replaced the valve cover thinking it was the PCV valve, but again, the squeak is still there. I then did the PCV valve/Intake manifold mod, and again, it's still squeaking! Also while having the intake removed to do the PCV mod, I also ported the intake manifold.
The squeak seems to get worse when the AC is on -- perhaps because the engine is under a greater load?
Can anyone share some insight as to:
1) Why the engine would squeak;
2) Why there would be so much vacuum in the valve cover to cause the squeak;
3) Why removing dipstick and oil fill cap with stop the squeak;
4) Why the engine would stumble and idle rough when the dipstick and/or fill cap are removed
I'm grateful for any help and insight you may have.
Thanks,
Mike