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Author Topic: Air box drain question  (Read 5915 times)
steve5B
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« on: May 04, 2009, 05:54:29 AM »


  As formentioned in a previous post, "Make sure your drain tubes are not clogged or pinched", I was wondering does this pertain to

   every engine or just the 6V-92?


    Steve 5B....
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« Reply #1 on: May 04, 2009, 06:12:09 AM »

This would apply to all the DD 2 stroke engines  (53, 71, 92, and 149 series engines).  Jack
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« Reply #2 on: May 04, 2009, 08:51:16 AM »



    Jack, thanks for the reply, are these tubes the ones that are called "BLOW BYE" that hang down below the engine?

    I don't know anything when it comes to mechanics!


   Steve 5B.....
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« Reply #3 on: May 04, 2009, 08:57:40 AM »

Steve to answer your question, yes and if you do like I did and that was to make the tubes actually touch the ground, you won't get near as much mess on the back of your bus. The ground will wear them down to where they need to be! Since doing this, my bus and engine stays a lot cleaner!

Ace
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« Reply #4 on: May 04, 2009, 12:09:14 PM »

 just spreading oil on the waters
The DD factory fix is a container set up that collects the tube outflow.  Never saw that one but I have seen 5 pound coffee cans hanging off of the drain tubes.  Those collect the run off and let you dump it when needed.

Ace's idea is really great unless your engine is putting out a lot of oil.  In that case you might not want to have the oil messing up your driveway....or anyone's you might visit.  I would even give some consideration to not leaving oil in the Wally Mart hospitality suite.  Still, that method would keep your rig cleaner.

Just spreading oil on the waters

John
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« Reply #5 on: May 04, 2009, 12:21:58 PM »

   Jack, thanks for the reply, are these tubes the ones that are called "BLOW BYE" that hang down below the engine?
   Steve 5B.....
I think the "BlowBy" tubes are the ones from the breather on each valve cover (or single valve cover on an inline 6 cylinder). They are approx 1" in diameter. The air box drains are attached to the block towards the rear of the engine and under the exhaust manifolds on V block engines (not sure on inline engines).  Jack
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« Reply #6 on: May 04, 2009, 02:46:18 PM »

You are correct Jack they are "crankcase breather tubes" the slobber tubes on my 71 are plumbed back into the pan from the factory and work well.>>>Dan
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« Reply #7 on: May 04, 2009, 03:23:44 PM »

I wonder why we could not plumb the breather into the induction like this system does. I know many of you have gone to a different air filter than the original oil bath stuff. Or even just a cyclonic air oil seperator that drains back to the crankcase.

http://www.yachtingmagazine.com/article.jsp?ID=1000068942

http://www.walkerairsep.com/

Extra Extra
http://www.walkerairsep.com/news_article.asp?id=15
« Last Edit: May 04, 2009, 03:33:54 PM by Airbag » Logged
JackConrad
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« Reply #8 on: May 04, 2009, 03:40:51 PM »

Here is a labeled photo of the air box drain tube and the air box access covers on the passenger side of our 8V71. Jack

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« Reply #9 on: May 04, 2009, 03:59:38 PM »

hi,
i have an "official" detroit air box collector on my silver'92, works like a hot damm, no mess on the back end ever. there  is also a check valve fitting on each bank that opens  at a spec pressure.
detroit took off the lines connected to the oil sump- something to do with crap in the oil ,i think
i think i paid about a $100 for the kit whe i did  the major o/h on engine
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« Reply #10 on: May 04, 2009, 04:12:13 PM »

hi,
i have an "official" Detroit air box collector on my silver'92, works like a hot damm, no mess on the back end ever. there  is also a check valve fitting on each bank that opens  at a spec pressure.
Detroit took off the lines connected to the oil sump- something to do with crap in the oil ,i think
i think i paid about a $100 for the kit when i did  the major o/h on engine


Here is our homemade drain tank.  3" PVC with 2 barbed fitting for the rubber tubing to connect the slobber tube drains, a hydraulic tank breather and a drain petcock in the lower end.  How does this compare to the DD unit?


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« Reply #11 on: May 04, 2009, 04:22:44 PM »

jack,
your homemade tank looks pretty close to what i have from detroit.mine is a bit more compact, but is still going to work the same as yours .i just got lazy and didn't feel like building something that wasn't much anyway
george
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« Reply #12 on: May 04, 2009, 04:33:01 PM »

jack,
your homemade tank looks pretty close to what i have from Detroit.mine is a bit more compact, but is still going to work the same as yours .i just got lazy and didn't feel like building something that wasn't much anyway
George

OK, having never seen the DD unit, I was just curious whether mine was similar.  Thanks, Jack
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« Reply #13 on: May 04, 2009, 06:28:37 PM »

My airbox drains, like Ace's, also are rubber tubes going all the way to the ground.

This takes care of the oil on the bus rear but still makes a mess in my friend's driveways so one day I plan to make one of those neat PVC drain collectors.
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« Reply #14 on: May 04, 2009, 06:47:26 PM »

Looks like those tubes could get clogged pretty easily.  They also look maybe not so easy to get to.  Guess I'll have to dig into things and see what the story is, then hope that fixing them solves my start-out problem.
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4104GA
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« Reply #15 on: May 04, 2009, 07:44:40 PM »

Jack your drain system is very close to the system I have on my 6 71 in my 4104.  Works great and really helps
to stop most of the crap on the back of the bus.
Sam
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bottomacher
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« Reply #16 on: May 05, 2009, 06:02:48 AM »

How often do you have to drain the tank? It looks like it would hold over a gallon.
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JackConrad
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« Reply #17 on: May 05, 2009, 06:25:26 AM »

How often do you have to drain the tank? It looks like it would hold over a gallon.

We drain our about once a year, never get over a cup or 2 our of it.  Jack
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« Reply #18 on: May 06, 2009, 07:03:12 PM »

It should be noted that jack's picture does not show the air box drain tube check valve. His is just a 90 degree brass connector going into a tube. My 8v71 has an actual check valve with a spring and ball on both sides of the motor. The check valves are supposed to close around 800 rpm. The rationale being you want it to slobber at idle but not when you are putting your foot into it. Jack, I made an identical set of PVC slobber tubes. I was surprised how little my bus was slobbering to make that big of mess all over my toad and the back of my bus. It must vaporize at speed.

Rick
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« Reply #19 on: May 06, 2009, 11:02:02 PM »

I'm not sure DD ever actually made one, but they commonly installed a system made by Walker Engineering.  Here's what it looks like, with enough information for you to make yur own:

http://www.walkerairsep.com/pdf/installation/Airbox%20Drain%20Kit%20AJ4120KT.pdf

tg
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« Reply #20 on: May 07, 2009, 03:20:20 AM »

Jack, Do you happen to have detailed instructions with photos on how to build one? That is something I would like to do, just don't know the correct way to go about it!

~Paul~
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« Reply #21 on: May 07, 2009, 05:02:30 AM »

Paul,
  A section of 3" PVC pipe (length to be determined by mounting location, approx. 12-16"), 2 end caps, 1 hydraulic tank vent, one 1/4" drain valve, and two 1/4" barb hose fitting (only one shown in photo).
  Drill and tap 2 1/4"  holes in top for the barb fittings, and a 3/4" hole for the breather. Drill & tap a 1/4" hole in the lower area of one of the end caps for the drain. Install all fittings and glue end caps in place, making sure the drain is near the bottom.  We attached the tank to the bus frame with a hose clamp.
 
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« Reply #22 on: May 07, 2009, 09:53:45 AM »

I have no exposure on this subject other than actually seeing those coffee cans hanging off of the bottom of the engine that collect the drain tube outflow.  It looked discouraging, honestly. 

Now reading this thread some things are making sense.  That comment about the check valve being open a idle and closed at operating rpm caught my eye.  Are those check valves, the ones that need replacing every 500 operating hours, EVER being serviced by most?  If the air box is loading up with "oil", is that the reason why these engines sometimes SMOKE AT STARTUP?  I guess my question is "DD went to a lot of trouble to incorp this design feature so it must have a purpose.  What is the symptom of this check valve being plugged or even stuck open, for that matter?  Inquiring minds and all that.

Thanks,

John
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« Reply #23 on: May 07, 2009, 11:05:49 AM »

Jack, Thanks, I'm going to copy it add that to my list, save it for the future when I have nothing to do! Roll Eyes OK with you? Wink

~Paul~
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« Reply #24 on: May 07, 2009, 11:07:33 AM »

save it for the future when I have nothing to do! ~Paul~

Paul,
    You own a bus, that will never happen!!! LOL  Jack
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« Reply #25 on: May 07, 2009, 11:54:45 AM »

Your question was:

What is the symptom of this check valve being plugged or even stuck open, for that matter? 

The symptom that it is stuck open is alot of oil all over your tow vehicle and the back of your bus with no other leaks to attribute it to. 

If it is clogged I would imagine if your bus is dumping a fair amount of oil into the tubes due to blower seals, or cracked or worn oil rings that you would find your motor a bit reluctant to come back to idle after letting off the throttle, due to it burning the built up oil in the airbox. Our two strokes will run on motor oil. The check valves are there to help prevent runaway motors.

One of the possible reasons for  a DD smoking at startup is due to excessive oil being in the airbox and draining into the cylinder, My bus doesn't smoke at startup it smokes blue for a short time after it has been idling, the general consensus on that symptom is a cracked oil ring or blower seals. Neither of which neccesarily has to be due to high mileage since your las overhaul. It is my understanding that it is not difficult to damage rings on these motors during overhauls and the blower seals don't like long periods of inactivity and are subject to brittleness due to age.

That's my two cents worth... which won't buy you a wodden nickle.

Rick

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