6637 malfunction, minor dusting
Senior User
Joined: Mar 2001
Posts: 497
Likes: 0
From: KC MO
So what's the difference as far as the seals go with a little pressure and a little vacuum? I would think that under max boost, there is a lot of vacuum being pulled on the CC. Maybe the blow-by cancels the vacuum?? I'm just wondering if it's all just splitting hairs in the end. I MUCH prefer a little vented fumes over nasty, oily intake parts, but that's just me... 
With no vacuum source the vapors only make their way out of the crank case when the pressure inside (blow by) is greater than atmospheric on the outside. End result is constant crankcase pressure.
With a little suction (or a lot, but I'm not a max boost very often) the inside pressure is relieved to some degree and the vapors have an easier time getting evacuated. End result is less crankcase pressure than above (maybe even close to zero). This does result in some oily intake parts over time, but that could be addressed with a proper catch can (at the expense of adding an extra maintenance item, whenever it needs to be emptied).
Post Fiend
Joined: Feb 2007
Posts: 14,541
Likes: 2
From: Dallas-Ft. Worth
I see what you're getting at. But where is it getting fresh air from then? If you pull a vacuum down on something, there is just less of whatever's in there by density. If you get fresh air in there from somewhere, that would be bad... That means water can get in too.
Either way, I don't see it being *that* big of a deal... Just my (not-so) humble opinion. 
Either way, I don't see it being *that* big of a deal... Just my (not-so) humble opinion.
Posting Guru
Joined: Mar 2008
Posts: 1,734
Likes: 1
From: Monroe VA
Just to throw this out there...
I have my CCV vented to the back of the truck. I was behind it today hooking up my boat and noticed the vapors smelled a bit different than what I'm used too. I did change my oil this past weekend, so maybe thats it. Call me crazy but I'm getting used to the smell and kinda liking it. With my CCV run to the rear of the truck I hardly ever smell it inside the cab. The wind has to blow just right. Also running it this far back you have to be careful of the bends in your hose, and keep check and make sure that oil doesnt stop up the hose. I used to have a catch can with some filter media in it and had it returned to the air intake and, one day i noticed that my IC pipes were starting to get a bit of oil on them so I switched back to the vent to the air method.
I have my CCV vented to the back of the truck. I was behind it today hooking up my boat and noticed the vapors smelled a bit different than what I'm used too. I did change my oil this past weekend, so maybe thats it. Call me crazy but I'm getting used to the smell and kinda liking it. With my CCV run to the rear of the truck I hardly ever smell it inside the cab. The wind has to blow just right. Also running it this far back you have to be careful of the bends in your hose, and keep check and make sure that oil doesnt stop up the hose. I used to have a catch can with some filter media in it and had it returned to the air intake and, one day i noticed that my IC pipes were starting to get a bit of oil on them so I switched back to the vent to the air method.
