I hate being so ignorant about Detroit Diesel engines, since there are so many buses that use them. :) My only other experience is with a Cat diesel.
I have read a little about the 'slobber tubes' on Detroits. In a nutshell, what are they there for? Mine leaks (what I would consider excessivly) on the drivers side. That same side of the enging exhaust also smokes a little while warming up.
When I took a recent trip, I inadvertantly used Dello 400 15-40 oil (about a gallon and a three quarters) could this have caused the extra 'slobber'? ???
What kind of problem will result in using the wrong oil? :-\
thanks for the input
Mark
Well, In a nutshell....
A 2-stroke detroit will not slobber with 15w-40 it will simply DROOL-N-POOL and spit oil out of places you didn't know you had. Some are better than others.
As for the tubes, They are called slobber tubes but are really air-box drains and they drain off any excess oil and junk from up in the Valley of the blower section. Stuff collects up there like blowback oil and fuel residue and dirt. The drains are supposed to have checkvalves that let the higher pressure in the air box under the blower push the excess out.
The drains also tap off unburned fuel and oil that leaks past the rings. Too much idleing and fast idle or cold running before the rings heat up will cause some loss.
First thing to do is to remove the check valves and wash them out with Kero and make sure they are working and then reinstall them.
If you have smoke until warmed up, You may have a cylinder with a poor compression or bad compression ring or oil control ring. When warmed up the ring swells up and seals better so the smoke goes away. This usually indicates its almost time for rebuild. Try cleaning the checkvalves first, Get the right oil in the engine and run the heck out of it down the road to clear out the excess oil and fuel that has collected in the engine.
That's my story... Good or Bad, I had one that fogged the road for the first 20 miles and cleared up on long trips.....Not anymore though....
Dave....
DD sells a kit (at least they used to) to fit on the tubes and catch the slobber. Do not, under any circumstances plumb it back into the air intake. It has contaminants in it that could harm your engine. Many people also make their own catch container out of half gallon jugs. The container can not be a sealed device. Others may have more details.
Richard
Valves on the air box drains only became standard on later model engines so you may not have them. If you have them, they are not a normal check valve, but a pressure controlled valve. With it in your hand, you can blow gently through the valve, but if you blow hard it shuts off. This allows the air box to drain when the engine is off or idling but closes when the RPM is raised. If it doesn't work in this fashion, you may be able to wash it out with solvent or it may have to be replaced.
You can probably find one of the factory style cannisters that mounts across under the engine
that has the two connections for the tubes that you run hoses to and a center capture drain.
Most all of the Ex-New Jersey MC9's had them and anyone salvaging any of them may still have one laying around.
Otherwise a 3" diameter 18 inch long piece of PVC with 2 caps on the ends and a hole drilled on each end for the tubes to drain into will work. a hole on the bottom with a 1" bit of pvc glued in so it sticks up into the pipe a little is the vent. when the pvc pipe fills up to the level of the inserted tube the overflow drains out. ( usually going down the road )....
Or one or a pair of gallon jugs tywrapped to the frame beside the engine works too! Just route extenstions to the hoses into the bottle...( same theory but not as nice looking . )
Whatever you decide to do, Please don't send that dirty oil and trash back into the engine oil pan.
You won't be happy with the end results when the engine gets trashed up.
Flame On, Flame Off.....
That nice film of oil on the back of your bus makes it go faster! ::) ::) ::) ::)
Asking a question for a friend, the below picture is of what I believe is the slobber tube for a 6v92TA in a 1986 102A3. I know what is marked to the left is the slobber tube off the valve cover, I just want to make sure the one to the right is also a slobber tube. It goes down by the starter and is just open.
Also, what's the consequence of tying the smaller one on this side to the other one on the other side of the engine?
There is a slobber tube with a check valve coming out of the airbox (not the valve cover) on each side of the engine. The stock tubes just end below the engine and dump their nasty stuff when the engine is idling or off. As already mentioned, to avoid making stains on someone's clean driveway, install catch cans or bottles to hold the spittle until you can dump them.
Houston Metro buses had the air box drains tied into the muffler I thought that was unique but wondered what happen when the engine got tired ,you shouldn't have but a few drop if the engine is healthy
Interesting. Exhaust back pressure would block them off off idle.
A couple years ago my 8V92TA got to dropping oil out tubes, big time. Blowing a gallon out the tubes in a 250 mile trip. Diagnosed "Blower Seals" . Had Blower R&R'ed and back to no oil out tubes. Guess there are many things that could cause it, this was mine.
It's the two stroke version of crankcase venting..>>>Dan
Air box drains have nothing to do with the crank case ventilation on a 2 stroke
They do the same job of removing unwanted substances from the engine core.>>>Dan
That's true to a point but it is a pressure system not a vent
I fixed my problem with a newer engine. :) Now only have a drip or two. I did hook my catch cans back up only to keep the toad cleaner. If they are draining like mine were time to fix something.
John
Aren't the crankcase vents using the crankcase pressure to vent.?? >>>Dan
Quote from: luvrbus on December 14, 2019, 07:52:21 PM
Houston Metro buses had the air box drains tied into the muffler I thought that was unique but wondered what happen when the engine got tired ,you shouldn't have but a few drop if the engine is healthy
If the Metro buses had rest rooms, they could have added that liquid to the exhaust as well, GM style. :o
air box and crankcase are two different areas completely separate from each other on 2 stroke. The air box is your pressure area before entering cylinder. Crankcase operates at neutral pressure. Air box over 6-900 rpm is you intake to cylinder should be boosted by blower at that point.
After dealing with two stroke Detroit's for 30 years ,,I understand the princibles of operation..My point being that both systems do basicly the same job even tho not connected other than sharing the same block..>>>Dan