Crankcase pressure questions

[gnathv]

When I installed my used turbo I ran it without the CDR connected. This caused oil to be pushed by the turbo seals and the turbo base grommett. I thought the used turbo had bad seals until I used this troubleshooting chart from J&H Diesel. Hope this helps. http://www.jhdiesel.com/failurechart1.htm

 

[6 Nebraska IDIs]

You cannot leave the CDR on the engine if you're running a RDT from another point on the motor. You must remove the CDR and only have one exit for the crank pressures. I've done all my RDT and crank evac systems this way and never had a problem.

 

[65sixbanger]

So what do you do with the CDR? On the BANKS it is mounted on the air box, so there will be a whole in the intake. Maybe I can cut a piece of flat stock with some holes and cover that hole up.

 

[Agnem]

OK lets review some basics here, because I'm hearing some things that need examination. First, when you install a turbo the factory CDR fittings get plugged. If you didn't do anything else, you'd have an unvented crankcase, which is majorly bad. The weak spot in a setup such as that, would be the turbo drain, and all the crankcase presure is going to head for that spot, and the dipstick. Under such circumstances, the presure would push oil and gas out of the grommit. It's not inconceivable that the restriction in oil flow might not cause oil to push out of the turbo seals and who knows where that's going to go. Now, if the install is done correctly, the CDR will be relocated and presure will vent either at a valve cover, or at the IP housing. If you want a road draft tube, the hose just vents to atmosphere. If you want a CDR, it goes to that, and then the CDR re-connects somewhere in the air intake. If there is any doubt that your crankcase is not vented properly, take your oil fill cap off and put a screen over it. This is not too dirty on a 6.9, with the oil fill off the front of the gear housing, but the 7.3's will get a lot of oil sling due to the placement of the opening. Now, the other issue with oil leaks and turbo drains, is the proper ventalation of the turkey pan. Early turkey pans that were designed for non-turbo engines, needed to have their internal baffle ventilated with an ice pick. If no holes, or not enough holes were made, you can get oil overflow from lack of draining. Replacement turkey pans are all set up for turbo's and have the proper drain built in. I would pull your turbo and do the hot oil test I mention in my turbo install article in the Tech Articles section.

 

[65sixbanger]

Ok Thanks Mel. I just replaced that Grommet that sita in the turkey pan for the drain so thats good for sure. In a different post they talk about making sure that plug behind the drain is sealed so I think I will do that. And if that doesnt do it then I will do the hot oil test.

 

[97idi]

in my case it pumped the oil out the rdt i had set up, and i didnt have my cdr removed so i think that was the proble i would remove urs or plug it some how

 

[65sixbanger]

I just got to thinking.. On the rebuild, I used a brand new FEL-PRO intake gasket so I shouldn't need to poke holes right??

 

[6 Nebraska IDIs]

I do it anyway. I figure its only 30 seconds of my time to put a couple holes in the bottome of the valley pan. I put 9 in my brown trucks VP.

 

[RLDSL]

Some pictures of your setup would be worth a thousand words here.
You will not need to perforate the new Felpro valley pan, it is already turbo spec, as are all the valley pans made after the turbo engines came into production
Belching oil with a road draft tube is not uncommon,Unfortunately since you just put the Banks kit on, that means a K&N air filter so you just compounded the problem where it is going to want to eat oil with the CDR in place as well. Assuming that your CDR is a functioning unit, When you put a free breathing air filter on, you mess up the balance that the system was designed to operate on to keep the crankcase gasses properly scavanged. Ford and International are strangely silent on the CDR leaving folks wanting to ditch the things, but GM having the same exact crankcase pressure control, is a bit more vocal in their manual and someone was nice enough to share it here

Once you lower what little vacuum you have by changing out the filter to a free breathing aftermarket filter, the system no longer functions as designed and can cause you to suck the crankcase dry ( ok not that bad, but you get the picture

When I had my shop open I worked on European cars, lots of diesels and would run into this all the time and I came up with an oil trap that I modified out of an Isuzu NPR diesel trucks breather system that would return the oil back to the pan for cars with free breathing air filters because of the excess oil that would always get sucked up into the breather line. COnstant complaint with EVERY car that had a free filter in it. Now for trucks you can get a breather filter from Racor CCV 4500 for about $250 that goes in the breather line and will return the excess oil to the pan automatically, or with a little welding skill, you can make something similar and just buy the check valve.

An alternative might be to rig a restrictor inside the air filter somehow to attempt to cut the flow back to that of a factory air filter where the breather system can function properly.

 

[Agnem]

Once you lower what little vacuum you have by changing out the filter to a free breathing aftermarket filter, the system no longer functions as designed and can cause you to suck the crankcase dry....

I'm not going to disagree with you, because it seems you have some experience in this area, but I would like an explaination of the science behind this. If I put two straws in my mouth, and one is open to atmosphere, and one is in a cup of water and I inhale, I only draw air through the one that is open. Likewise, if I restrict the open one, eventually I can draw water depending on the amount of restriction. Now I realize, the crankcase is presurized, so that's going to help push air, oil, or whatever up my theoretical straw, but explain to me how having an additional restriction on the one originally vented to atmosphere is going to LESSEN the amount of whatever I draw from the straw in the cup? Based on the GM article you supplied, the spring and diaphram just maintain a certain amount of presure in relation to the presure level in the "open" side of the intake. I'm trying to understand how increasing the available atmospheric presure (by removing any air filter restriction) is going to make that spring weaker. It seems to me, it would be the opposite, increasing crankcase presure if anything.

 

[65sixbanger]

Ok I will try to get pics up on here later tonight.
Thanks for all the help
-Lance

 

[65sixbanger]

I may add that this leak is not consistant at all. Some times when I park it leaks drop,drop,drop, etc... then other times it wont leak for hours. I can just write it off as my truck's period

 

[RLDSL]

I'm not going to disagree with you, because it seems you have some experience in this area, but I would like an explaination of the science behind this. If I put two straws in my mouth, and one is open to atmosphere, and one is in a cup of water and I inhale, I only draw air through the one that is open. Likewise, if I restrict the open one, eventually I can draw water depending on the amount of restriction. Now I realize, the crankcase is presurized, so that's going to help push air, oil, or whatever up my theoretical straw, but explain to me how having an additional restriction on the one originally vented to atmosphere is going to LESSEN the amount of whatever I draw from the straw in the cup? Based on the GM article you supplied, the spring and diaphram just maintain a certain amount of presure in relation to the presure level in the "open" side of the intake. I'm trying to understand how increasing the available atmospheric presure (by removing any air filter restriction) is going to make that spring weaker. It seems to me, it would be the opposite, increasing crankcase presure if anything.

That's where it gets interesting. Previously , breather systems were in place for the sole purpose of getting the blowby out of the crankcase to keep from blowing seals so a large diameter tube, larger in diameter than what anyone here uses for a RDT would be used to vent the gasses out and the draft of the road air passing under was enough to scavange the crancase gasses out and accomplish the job.

Then came emissions regulations and all bets were off and the purpose , design and function of the breather system completely changed. The purpose no longer was to just remove blowby gasses, but to A) keep the gasses retained in the engine and b) to burn the excess gasses and pressure off internally in the engine, while c) not increasing the pollutant output count of the engine significantly.
All of which is not an easy task to accomplish
If you notice from that GM manual , it states that the CDR is there to Maintain and regulate crankcase pressure, sounds counterintuitive doesn't it. In reality the system is designed to maintain very closely regulated crankcase pressures at specific rpm ranges. CAT engines use a very similar breather regulator on many of their engines

The thing is setup to suck just enough to pull the vapours and to apply pressure to cause as much oil vapour as possible to condense back to liquid so it will return to the crankcase INSTEAD of being drawn into the intake.
If you change a variable that the engineers so painstakingly worked out and put a free flowing air filter on there, the crankcase depression regulator, can no longer regulate and becomes simply an open hole that sucks oil through.

Even if you want to do a RDT, if you want one that will really function properly , you would need to open up the hole and increase the size by about half again at least for it to function as a proper RDT as the hole for the CDR was never meant to be used for that function and it's way too small to service as a proper RDT vent.

 

[65sixbanger]

So if I have two RDT's, one off the valve cover and on from the front of the IP cover, why did it throw oil everywhere when I left the CDR bolted up?

 

[RLDSL]

So if I have two RDT's, one off the valve cover and on from the front of the IP cover, why did it throw oil everywhere when I left the CDR bolted up?

In essence with them both attached, with the open nature of the air filter the opening at the CDR was doing nothing, there would be zero draw at that point so the only functioning breather would be the RDT and if it were not properly installed that's a dead end.
As Mentioned, for one to truly function it would need to be larger, but even allowing that, a RDT needs to be mounted to where it exits below the lowest point of the vehicle at a right angle to the road to where the passing air maintains a continuous draw on the tube to scavange the gasses ( hence the term Road Draft, as in, to be drawn out by the road )to prevent pressure buildup or a belch will occoure .

There can be other things at play as well . You mentioned it being rebuilt, How long ago was that?