How much should my bus be slobbering?

[Jerry Liebler]

Think about the airbox and what where it is, it is between the blower and the cylinders, pressurised by the blower.  How does unburnt fuel ever get there?  A bit if oil gets there by the rings scraping it off into the ports.  Detroit made kits to connect these drains to the crankcase, they never recalled them!  These kits included check valves. The drains connected to the crankcase were required, for some time, in California.  Several busnuts, including me, have them connected to the crankcase and have observed no ill effects.  One busnut has 20 years and over 200,000 miles on such a connection.
Regards
Jerry 4107 1120 

[Joebus]

Thanks for the info, the application I seen was in a GMC, with a V drive.
Should the air coming from my engines tubes appear to have a fairly high pressure? (8v71T with N75s) This engine has 70 hours since a complete rebuild (pistons, sleeves, injectors, valves, etc)

[makemineatwostroke]

Joe, i  wouldn't worry about the air pressue now it takes around 20,000 miles for a break in period for that engine after a major over haul.Do you have the check valves on your drain tubes

[akroyaleagle]

Paladin,
I have noticed that you like the rest of us at some time have many questions about the beast.

I've been down the road of plumbing the slobber tubes into the oil pan and the air intake on my old 8V71N based on advice I received from other BusNuts before this board.
My advice is don't do it.
Put a rubber hose on each tube and run them to a used oil or antifreeze container placed in the engine compartment or generator compartment.
You will be surprised how little fluid you gather. A little goes a long way on the floor.
I have had the 92 since 2000 and have never emptied the antifreeze container. It never has more than a couple tablespoons in it and that evaporates leaving only a little carbon.
As someone said below,it's dirty fuel not oil. That doesn't belong in the oil which is why the tubes are there in the first place.
If the check valves are working correctly, they need air pressure to open. That means they are normally CLOSED. They open when there is sufficient blower pressure to compress the spring and allow the drain to function. So there should never be more than a small spot anyway.

If you send me an email, I will forward you several documents that will raise your learning curve VERY high about Detroits from recognised experts.
Don't be afraid to ask, learn and get to know your bus and it's components.
There is a wealth of information here on the boards now that wasn't available when some of us were doing this. Most of us are still learning!
You will learn to sort the chaff.
Also if you post your email in your profile you will sometimes get offers of information that is too lengthy to post here.
Good Luck,

[makemineatwostroke]

Joe, thats a good post as I am a believer in the check valves only I don't even like the catch cans because you do away with one of the best diagnostics tools you could have.    example like you see antifreeze coming out of one side you know there is problem on that side,a lot of pouring oil out on one side another problem I don't use a can on mine if the check valves are working properly you get very little junk from the tubes because it forces the engine to burn it. But for FWIW the valves open at idle and when the engine is stopped only not when the pressure gets high this is why I recommend them for any engine with a turbo they will increase your boost a few pounds over the open 1/4 in tubes with no valves

[Busted Knuckle]

Think about the airbox and what where it is, it is between the blower and the cylinders, pressurised by the blower.  How does unburnt fuel ever get there?  A bit if oil gets there by the rings scraping it off into the ports.  Detroit made kits to connect these drains to the crankcase, they never recalled them!  These kits included check valves. The drains connected to the crankcase were required, for some time, in California.  Several busnuts, including me, have them connected to the crankcase and have observed no ill effects.  One busnut has 20 years and over 200,000 miles on such a connection.
Regards
Jerry 4107 1120 

Jerry,
As much as I respect you and your knowledge and opinion, on this one I have to disagree! I know for a fact that they did infact recall them as they were afraid of antifreeze accidentally getting into the crank case (as makemineatwostroke points out). I do apologize for forgetting the exact reason until he mentioned it. And I will make it a point to located and scan and post the service bulletin & a copy showing that our first SETRA (an '89 w/8V92TA DDEC) had in fact been thru the recall and a catch can installed under the center of the oil pan. As a matter of fact I just saw the old catch can today in the shop (as I robbed it off the bus when we sold it!) The reason they were installed &/or reccommended was in case of a head gasket or after cooler leak, it would not get into the oil and destroy the bearings! I don't usually have any reason at all to disagree with a man of your skills & knowledge Jerry, but on this one somewhere here in all this crap I have the proof (unless it ended up in the stuff we gave the new owner such as service records and such!). Thank you and have a great day! I also believe TomC might be able to verify this as I think his was also recalled (in his big trk!), but I'm not positive on that either! FWIW   BK  aka "he young smart @$# that knows nothing"

[Jerry Liebler]

BK,
   I'm waiting for the documentation.  Isn't the 8V71 a dry sleeve engine?  How could coolant get into the airbox without very serious other problems?   I did research this about 3 years ago when my engine was overhauled and found 3 different service bulletins advocating the drains to the crank case and none asking for their removal.
Regards
Jerry 4107 1120

[jackhartjr]

Jerry, some were dry sleeve, some were wet sleeve.  I can't remember which were which.  When I find the answer I will post it here.
Jack

[makemineatwostroke]

Jack, all 71 series are dry sleeve, the 92 series and the 53 series have coolant that comes in contact with the sleeve  fwiw 

[makemineatwostroke]

Jerry, the 71 series is a dry sleeve engine but with a leaking or cracked head or a bad injector tube they will get as much coolant in the air box as a 92 series FWIW and  have a great day

[jackhartjr]

You know folks, sometimes in ones life they say the stupidest things.  Why I said the 8V71 was wet sleeve is beyond me.  Sorry!  And thanks to all that straightened me out.
Jack

[Jerry Liebler]

I don't  see how air box drains are going to help an engine with a cracked head.
Regards
Jerry 4107 1120

[Sojourner]

I don't  see how air box drains are going to help an engine with a cracked head.
Regards
Jerry 4107 1120

Jerry...I respect you always and appreciate your many help on board.

Leaking head gasket and/or crack head in intake. I have experience cracked head that leaks in exhaust passage to cause coolant to get into intake passage to manifold to nearby intake passage into non leaking cylinder as well. While it shut down for overnight and then is accumulate enough moisture into droplet. Which mean that it will get into ports chamber to drain passage. If that is connecting to crankcase then you know the rest of the story.FWIW

Sojourn for Christ, Jerry

[Busted Knuckle]

BK,
   I'm waiting for the documentation.  Isn't the 8V71 a dry sleeve engine?  How could coolant get into the airbox without very serious other problems?   I did research this about 3 years ago when my engine was overhauled and found 3 different service bulletins advocating the drains to the crank case and none asking for their removal.
Regards
Jerry 4107 1120

Jerry,
I will post it when I find it again! Right now I don't even have the time to look! But I was refering to the 92 series (I don't and never have owned a 71 although in my uncles opinion they were the best ever!) And yes I still stick by my statement that Detroit did infact remove all the drains from the oil pans on units that were brought in on the very limited publicized recall. When we bought #702 (fleet #) we found the recall paper, along with a work order from the DD shop that did the work, and a copy of the later issued service bulletin order on the subject. Again I didn't mean to imply that it was for a 71 series. But the service bulletin clearly stated that "failure to remove the airbox drain hoses from the crank case/oil pan could and most probably would cause a bearing failure in the event of a head, gasket, injector, or aftercooler malfunction"! (may not be exact wording but it is very darn close to what the service bulletin I read said!) And again when I have some time I will go down to the shop and dig thru my old desk where I believe those papers may be. Also please note I do respect your knowledge of these buses very much! And I would never flat out argue with you or anyone else about it had I not read the papers from DD myself. I hate being wrong, and I damn sure hate to admit it when I am. Which is why I try not to say, what I don't know!
  BK 

[Paladin]