Hello everyone, I was out messing around with the bus yesterday 79 MC9 8v71, and noticed a pretty steady oil drip coming from a tube coming out of the side of the block. We are taking out on a trip next weekend about 175 miles one way and don't want any unexpected problems so I was wondering if someone might be able to tell me if this a major concern or not? I am going to attempt to include a couple pics so please bear with me! These tubes, one on each side come out of the side of the block towards the rear of the engine an elbow comes out of the block then there appears what might be a check valve of some sorts and then approx 3/8 dia. copper drain tube. I haven't noticed this leak before but not to say that it hasn't always been there the one leaking is on the drivers side and is a pretty constant drip. Is this a common natural leak or is this a potential problem? Don't want to be pumping all our oil out unknowingly while driving.
Thanks, Billy
Ahh, the first time you find the "slobber tubes"...second only to the first time you find the emergency shut-down flap has tripped itself. More has been written on Detroit's "marking their territory" through the slobber tubes than anything else about them, I swear. They are correctly called air box drains, and they allow fluid buildup in the air box under the blower to drain away. What happens is the blower pushes air into the air box, which is then pushed into the cylinders for combustion. Oil can get into the airbox from blower seals or from oil bypassing the oil control rings on the pistons, and more often you get unburnt fuel coming in from the cylinders themselves, especially at idle when combustion is poor. When an engine gets older and the piston ring seal is getting poor, you tend to get more fluid. The unburnt fluid mixed with some soot and a little oil is very black and dirty and looks just like an oil leak. The check valves are designed to close at around 2 - 3 psi of positive pressure inside the airbox, which is usually achieved at around 700 rpm, so the valves seal and air/fluid is not supposed to come out when the engine is running above idle. You can replace or clean the check valves, or take them off, it doesn't seem to matter much. You can route hoses from the copper tubes to catch-cans if you don't like leaking all over the place where-ever you stop. If you have excessive slobber you can start to save up for a rebuild - typical reasons are leaking blower seals, bad compression, bad oil rings, all that sort of bad stuff. Excessive idling of the engine (more than 10 minutes) will really contribute to slobber. Some people don't like to call it slobber, but I think it's a good word, very descriptive and I like it (the word, not the slobber)
Brian
Those are "Slobber" tubes. (airbox drains)
Those are one way check valves in them.
Most old buses (and a few later ones) with the two stroke motors drain through them and leave various size puddles on the ground under each side of the motor, depending on the wear stage of the engine. The puddles may be the size of dimes or much larger.
The check valves are worn out or dirty.. You should replace or clean them when it's convenient. It is not something that has to be done now.
When the engine is started and the airbox pressurizes, the valves should close.
When the engine is shut down and the pressure stops in the airbox, the valves should open and drain.
Most folks put rubber lines on the ends of the tubes and route them into any old container. I use a empty antifreeze bottle.
It's been there since the new engine was installed in 2000 and has never caught anything.
Your driveway and those of your friends and neighbors, rv pads and parking lots will look much better if you collect the drainage.
While I was typing, Bevans6 also answered your questions. I'll post mine also to reassure you. Continue your plans and be a good neighbor when you get back.
Thank you guys for the info and advice!! Dummy me I wondered about those possibly being the slobber tubes but had let someone else convince me that the larger tubes coming down from the center of the valve covers were the slobber tubes! Guess I can't learn much if I don't ask. Thank you again for taking the time to answer these silly questions, you guys are great hopefully someday I can return the favor in some way!!
Thanks again, Billy
They are not "slobber tubes"-- they are correctly called air box drains. I think of slobber as a person who drools or spits on everything, probably not their fault. However, Detroits are not humans. Totally disgusting. Oil comes out of the air box drains along with moisture and a little fuel as a by-product of the 2 stroke design. A correctly running Detroit 2-stroke will have very little oil coming out those tubes. So you either have a problem or possibly have let your engine idle to much which lets the oil pass past the oil control rings.
http://www.thefreedictionary.com/slobber (http://www.thefreedictionary.com/slobber)
slob·ber (slbr)
v. slob·bered, slob·ber·ing, slob·bers
v.intr.
1. To let saliva or liquid spill out from the mouth; drool.
2. To express sentiment or enthusiasm effusively or incoherently; gush.
v.tr.
To wet or smear with or as if with saliva or liquid dribbled from the mouth.
n.
Billy -
You've been given good advice by all of the above, I'd like to add to that a little.
When you said you were out "messing around" the engine, I take it that the engine was idling.
Most buses have a fast idle switch, is yours operable?
Best way to create a LOT of gunk coming out the air box drains is to let the engine idle at the low speed setting. Flip the switch to fast idle, and the amount is reduced considerably.
However - the worst thing you can do to a Detroit is to let it idle with no load on it. If you're not going to get in the bus and go somewhere, don't even start it.
Fire it up, flip on the fast idle switch, do your pre-trip inspection, then drive off. And drive it 50 miles or more to thoroughly get all the moving parts happy again.
Your Detroit will like you much better!
FWIW & HTH. . .
;)
Geoff, RJ,
Great info, yes my fast idle is operable, and yes I did have the engine idling but for some reason I did not think to kick on the fast idle, I usually do but for some reason I just didn't. I have been replacing some air bags and chasing a couple air leaks so I have idled more recently than I would like in order to get the old girl up in the air enough to get a jack under her. So this makes sense and hopefully a great lesson learned! :) I will keep an eye on this during our trip and devise myself a catch can so I am not making a mess everywhere we go.
Again Thank You to everyone who took the time to help me out with this issue the knowledge and information is Greatly Appreciated!!
Billy
I don't care for the term slobber tube my self but people call the drains slobber tubes the saying must have come from a truck driver they have a name for everything no offense intended drivers
I have fun when people tell me the slobber tubes or puke tubes are spitting oil I just ask what ! and where exactly are they located as I never heard of one like Geoff they are air box drains to me
good luck
Quote from: Bussman84
I will keep an eye on this during our trip and devise myself a catch can so I am not making a mess everywhere we go.
Billy
Billy a simple catch can is to put a pop bottle on each drain tube.
Or some use a rubber hose to run them over to the side and use a gallon jug.
Also some guys go all out and fabricate fancy catch cans out of PVC pipe (and other materials) with sealed lines, fittings, vents and a drain too!
;D BK ;D
See, I told you someone would object to slobber tubes - and even after I made a point of putting the correct name - air box drains - in there as well. As far as I'm concerned the engine is drooling, so they can be quite reasonably called slobber tubes. If you have no sense of humour, then you should also remember that the engine is a Detroit Diesel two cycle engine, not a Detroit two stroke. There's proper names for everything, and then there's what people actually call them...
Brian
Buy the Walker catch cans they are not that expensive for a 2 stroke or 2 cycle kit #AJ 4120KT comes with everything to install and ask for the air box drain can or they will have no idea what you are asking for
Endless amounts of great information and great people on here!!! Thank you all so very very much!!!
BK the pop bottle trick sounds like a quick easy thing that I can get done before we head out Friday.
Luvrbus I checked out the walker kit this afternoon looks like a pretty neat set up. But I wasn't having much luck finding where to buy one, is that something I should go to my local Detroit shop and ask for? Or maybe Luke?
Thanks again, Billy
Next time you have digestive problems, we will call your drawers "slobber underwear".
Quote from: bevans6 on April 15, 2013, 09:32:34 AM
See, I told you someone would object to slobber tubes - and even after I made a point of putting the correct name - air box drains - in there as well. As far as I'm concerned the engine is drooling, so they can be quite reasonably called slobber tubes. If you have no sense of humour, then you should also remember that the engine is a Detroit Diesel two cycle engine, not a Detroit two stroke. There's proper names for everything, and then there's what people actually call them...
Brian
Geoff and Clifford:
I have the great luck to personally know both of you.
I assume most don't.
The two of you are rightfully recognized by the members of these boards as gurus.
I have tried to keep my fingers from entering this game but I can not control them.
All items in life have a proper name. Many of them are known by other names.
Some of us included both the proper name and the widely used nickname for these tubes in our posts.
This is pole vaulting over pissant hills! And it tends to turn off folks new to our madness.
The older I get the more I tend to "slobber" in my underwear.
I believe everyone understands that term, even if it's not funny to some.
It doesn't bother me as much as some I assure you Joe and Geoff is not as bad as some others I know but I was always taught they were air box drains and it never changed, for me the term puke tubes does bother me though
Fwiw when I was at Ft Hood a few months ago I was amazed at the young men and women that called it air box drains for me to get upset with people calling those slobber tubes it's not going to happen in this life time
good luck and tell Frankie hi for us
Well, Akroyaleagle and I both actually answered the question and all Geoff managed to do is piss on us. "nuff said.
Brian
Thanks Clifford!
My comments were only meant to point out how perfectly good questions and comments are jacked out of proportion.
It seems nearly every thread gets hi-jacked somehow.
Most of us that have been around longer than these boards have thick hides (or heads).
Some newer folks may not. That's probably why they lurk and do not enter the fray.
Maybe the folks that run this board will start a new area called "RANTS" or something like that.
Can we all just pull up our big boy pants and move on?
I saw Bevans6 last post on Face Book. BCM has excerpts from various posts posted from time to time. That peaked my interest to re-read this thread.
I'm more upset with what happened in Boston than worrying about what something is called. Slobber tube is slang, and most of us know it. As was pointed out, both terms were used.
Let's keep on track and keep the good discussions going.
Quote from: bevans6 on April 16, 2013, 01:56:23 PM
Well, Akroyaleagle and I both actually answered the question and all Geoff managed to do is piss on us. "nuff said.
Brian
Brian, I think you need to re-read my posts on this thread. I have been working on Detroit 2 strokes since 1975, and this is the only place I have ever heard of air box drains incorrectly called "slobber tubes'. From a mechanical point of view, they are simply drains since the blower produces more air than the engine needs, and at the same time, excess fluids are blown out to keep the air box clean.
When someone says "slobber tubes" that indicates that the engine is producing excessive oil and that is what the tubes are designed for. Totally false-- If you have a lot of oil coming out the air box drains that indicates a problem with the engine. I guess calling the air box drains "slobber tubes" is a catchy term for laymen, but it really bothers a true Detroit mechanic like me (and Clifford).
I have been posting on this board since the the mid-90's, and I have always corrected people who use the term "slobber tubes"-- it is a disgusting term and incorrect in theory/use.
--Geoff
well said!!!!!!!!!!!!!!
Well, I have been feeling a bit guilty for a long time about not replacing my air box drain catch jug. This thread has at least gotten me a little motivated to do it. About what to call them, sometimes seemingly clever names are given to things that are not really very accurate. A "rice rocket", for example, has nothing to do with rice. Each of us can make our own choice of what terms we wish to use. However, I would just say that the term "slobber tube", although a very clear image, is somewhat of an insult to the engine and is best used when you are angry with it.
Show the old girls a little respect guys she been pushing the old buses and powering other things for 73 years now while other engines have come and gone she is still chugging away and will be for a long time to come
CARB and EPA have both tried to make her go away but she just keeps on singing the same lullaby like no other can imitate kinda like the Harley lol
good luck
For the know it all types, Do you remember when the air box drains were plumbed back into the crankcase, yup, crankcase, they did not drip on the ground.
Detroit old 2 strokers saved our bacon in WWII, no other engine would nor could.
Being a 2 stroke fanatic and having the most fun with a 12V-71 in a MC7 is as much fun one can have with their pants on.
Another reason I do laugh reading some of this trivia, I say get a life folks.
Very few take this as from the burning bush.
Dave M