Well, I never thought I'd have that in the subject line....

Anyways, I finally went to synthectic, Moblie 1 0W40, for the new 6.0 just a bit over 3000 miles.

So, I do everything as I normally have over the countless oil changes I've done over the years. Well, this time something new has occured. I dump 5 1/2 quarts (the other 1/2 quart is in the oil filter) of synthetic into the motor. Start the motor, oli presure a ~45 PSI. Check tranny fluid. It's good, the normal process so far. Turn off the truck, now it's time to check the oil. As soon as I pull the dipstick, I hear the sound of air rushing. WOW! This hasn't happened before! Oil level is good. Start truck the truck again, run it for about 45 seconds, oil pressure good at ~45. Turn truck off, pull dipsick at hear the sound again. To me, it sounds like it's rushing out, positively pressurized in the motor. Before I try this a third time to feel which way the air is going, I'm seeing if you guys have heard of this before.

I hear, what I think may be an old wives tail, that you should remove the oil dipstick when filling the engine with oil to prevent an air lock. I'll do this when I think of it (it can't hurt), but forgot to do it this time.

So, what the heck is going on?

 

Gremlins

 

OK, a little more info.

She's pulling one heck of a vacuum. I was showing my friend, so I pulled the dipstick while it was idling (~600rpms) and you can definateley feel the vacuum by putting you finger over the dipstick tube.

I was thinking that a cam (208/216 @0.50) may have an an effect, but that should be completely isolated from the crankcase and even if it was possible I would've seen this with my oil checks and changes during the break in period.

So, the only thing I've change is the type and viscosity of oil. I was running Pennzoil Dino 10W30 and switched to the 0W40 Mobil 1 mainly from Patman's info. I wanted to go with the German Castrol 10W30, but I was lucky to get a hold of the Mobil 1.

 

Your crankcase is connected to the intake manifold through the PCV system. That's where the vacuum is coming from.

 

So air rushes in when you pull the dipstick AFTER you turn the truck off?

 

Correct!

 

If you let the engine sit for a little bit is there still a vacuum on the dipstick tube?

IF a few things sealed up tight enough I could see a vacuum remaining in the crankcase for a little bit but, it should dissipate pretty quick.

The vacuum in the crankcase is normal while at idle and cruise.

 

Got it, I'll start it up again and check it after a beer.

 

Throw one back for me while your at it.

 

It's just a Foster's, Australian for beer, but made in Canada!

Well, 1/2 a beer later and no "whoosh", so i guess all is well.

 

Actually air isnt rushing in, it is releasing the suction is has on the engine, the vaccum could be caused from incorrect PCV setup, IE, i have a 98 car with a 99 engine, diff valve covers, = diff pcv, i rigged mine because i didnt have all the correct stuff, so i improvised, well, when my motor got warm it would squeel, REALLY loud, almost sounded likea throwout bearing, i tried EVERYTHING, i had no idea this is what it was, i replaced the slave thinking maybe rust or somthing, i took the flywheel off, replaced rearmain, took the crankpulley off replaced that seal, lubed everything, and it STILL did it, i finally went to check for blowby, and i couldned pull my oilcap off while the engine was running and making this noise, finally i grabbed a big pair of channel lock pliers and removed the oilcap, and as sooon as i did i heard SHHHHHHHHHHHHHHHHHHHHHHHHH, and the noise was INSTANTLY gone, i should do this and video it and post it, it would be a good lesson..

Not sure this is your problem, but a worth looking at..

 

Interesting info...It's a 2001 6.0l engine in a 200 vehicle. there is a slightly different PCV set up where the 2000 5.3 passenger side PCV connected to the TB and the 2001 6.0 PCV on the passenger side connects to intake manifold behind the TB. I have a BBK designed for the 2000 on the 6.0 so I had to block off that nipple on the BBK.

As for strange noises, I'm getting a chriping/squeeling from what I think is my PS pulley, but I really haven't islolated it since I only hear it while I'm coasting to a stop. I don't get any noise at idle or part throttle while driving.

Hopefully this weekend, the weather will be nice and the driveway will be dry so I can pull the PS pump pulley and reseat it. If it doens't go away I'll refer back to your post.

Thanks for the info everyone!

 

Heres what you do, when your engine warms up, pull a PCV line off of a Valve cover, and see if your noise goes away.. thats the way mine is. i will tryin get a video of my car making this noices, its seriously was a vaccum cleaner, when/if you put your hand over the oil cap it you such your palm in and leave a red mark, i will def tryin get vid

 

The intake manifold is sucking air outta the crankcase via the PCV valve. It is normal, nothing wrong at all. There should be around 9psi of vacuum at idle on a stock vehicle.

Here is the route the air takes.

Air is sucked into the valve cover through the fresh air vent on the passenger valve cover. Then the air makes it's way down into the crankcase the same way the oil gets back down there from the heads. Then that air keeps on moving along as it is sucked up the PCV system and back into the intake manifold. It is a closed system since the MAF has already metered the air that is being sucked down the fresh air vent.

Just think of the PCV valve that hooks to the intake manifold as one big line that runs through the bottom of the engine and up to the TB nipple(fresh air vent attatchment). Sucks air from in front of the TB blade all the way back into the intake manifold where the PCV line hooks up.

I can't explain it any better than that.

 

Yeah, we figured this and sat down and drew a picture. My drawing sucks, so it turned out looking like somebody, waist up, holding their hands behind their head.

I sure it's OK, but in all my years I've never seen/heard an engine hold a vacuum from the crankcase.

Another question, how is the oil sending unit reading a positive pressure if the crankcase is being vented via the intake and PCV? Is the Oil Pressure actually derived from this process?

Wow! I feel like a

 

I've never noticed my truck holding a vacuum like that. What did you plug up on your TB/valve cover? Maybe that has something to do with it.

The oil pressure sensor gets it's reading from the pressurised side of the oiling system, not from the crankcase.

I can really imagine your drawing look like that, that is what it should look like.

 

Just a soft rubber cap. Maybe it is from the motor swap, since I've only changed the oil once at the 200 mile mark and I may have taken a few minutes to check to oil level then. I'll report back after the drive to work tomorrow morning to see if she still sucks after 20 miles.

 

The little nipple coming off the TB should be attatched to the little nipple on the passenger side valve cover. If the line on you passenger side valve cover is capped and your TB blade is real greasy messy on the back it could cause the vacuum to take a while to equalize when the engine is off.

If that line is hooked up the crankcase should equalize with ambient pressure immediately and the dipstick wouldn't suck air in when the engine is off.

Hook that line back up and try it.

 

OK, right now, I have the passenger side pcv hooked up to the intake manifold. I'll try hooking it up to the TB and capping the intake nipple. Gotta love modifications

My TB Blade better not be all crappy! I just cleaned it and got rid of the EGR!

 

No, don't do anything yet cause you just confused the hell outta me. I need to go look at my truck and get back with you. I can't picture how yours is hooked up for some reason. Probably cause it's late and I'm tired.

Let's pick this back up tomorrow.