Engine makes a whirring or whistling sound until the dipstick is removed then the sound stops. No driveability issues. Can't pinpoint problem using a mechanics stethoscope. When I removed the dipstick I put my finger tip on the tube and it was sucked onto the tube meaning the crankcase is under vacuum. I know this is backwards. How could I have a vacuum in my crankcase instead of positive pressure? Where should I start looing for this problem. I have never heard of negative crankcase pressure. This doesn't make sense. This is a 2002 5.4

 

I'd start with a new PCV and see what happens.

 

THE NOISE YOU ARE HEARING IT A SEAL WHINING FROM THE VACCUME ON THE CRANK CASE.

 

the PVC valve in the right had valve cover is suppose to pull a slight vacuum on the crankcase to pull out fumes and burn the vapors... if the valve failes you could get excessive sucking... Thats the only thing that causes crankcase vacuum, otherwise it would be positive pressure from piston leakby.

 

After having thought about this a little more I know I have positive crankcase pressure due to blowby which is then turned into negative pressure by engine vacuum through the PCV valve. The thing is I haven't seen a vacuum strong enough to hold my finger against the dipstick tube. So when I put the dipstick back in and the whistling sound comes back the vacuum is still there and it's bleeding past a seal creating this sound? Are we talking about the front or rear crankcase seal, valley cover seal or rocker cover seal?

 

the PCV valve controls the amount of suction to just get a minimal vacuum in the engine. i would start by replacing the PCV valve, and looking at rubber rings and gaskets--- unless you can narrow down the location of the noise while in the driveway.

 

What about a smoke machine. Say we pull the dipstick and smoke the engine through the dipstick tube. Won't I be able to find the faulty seal by observing where the smoke comes out?

 

well, you have been told 3 times to change the PCV valve to control the suction on the crank case. I guess if you want to put smoke in it, or connect it to an air compressor, go for it.... tell us what you find.