Bakelly78
Member
After some thought and air box inspection, going to remove blower. Blower looked dry with a quick inspection, but suspect enough oil is getting by to cause this. Will update if that was it when finished. Appreciate all the help!!
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Detroit 6-71 wet stacking
- Thread starter Bakelly78
- Start date
RZucker
Senior Member
The pics of the air box look too dry to me. I doubt the blower is the issue. Just sayin'.
At this point I would look at 2 things. Position each piston in its liner ports where you can see the very bottom ring set. Those are you oil control scraper rings......new/good condition scraper rings have an edge on the outside of the ring. If it looks like its flattened out (similar to the compression rings above it) then your oil control rings are worn. Worn rings can be from just normal wear, dirty engine oil being run, or dirt infiltration through the air cleaner/ blower. The only fix for this is piston kit replacements.
The next thing is to remove your exhaust manifold. Look at all 6 exhaust ports and compare them with each other. Properly tuned Detroits (considering the compression is normal and even between all the cylinders) will look dry but carboned. If you see 1 or more that are wet with oil, those are your culprit cylinders. If they are all wet, you more than likely just have an engine that's is severely worn and needed overhauled.
What you are seeing in the airbox pics is normal on high hour engines. You may have some blower seal leakage, but in my opinion that is not what is causing your issue. Again, make sure your airbox drains are clear. When the engine is running, you should feel air coming out of them.
The next thing is to remove your exhaust manifold. Look at all 6 exhaust ports and compare them with each other. Properly tuned Detroits (considering the compression is normal and even between all the cylinders) will look dry but carboned. If you see 1 or more that are wet with oil, those are your culprit cylinders. If they are all wet, you more than likely just have an engine that's is severely worn and needed overhauled.
What you are seeing in the airbox pics is normal on high hour engines. You may have some blower seal leakage, but in my opinion that is not what is causing your issue. Again, make sure your airbox drains are clear. When the engine is running, you should feel air coming out of them.
Now that Ive had my second cup of coffee, I just remembered that I don't believe you can see the oil control rings in the liner port, the travel stops just short. Someone correct me if I'm wrong, its been awhile since I've done a 71 series. 
*NOTE* MY brain is dead today. Ignore this post lol Better yet...……...ignore everything I say today LMAO
*NOTE* MY brain is dead today. Ignore this post lol Better yet...……...ignore everything I say today LMAO
Bakelly78
Member
Yea, they don’t come up past the ports. Don’t think its the oil rings. Cylinders look good and no signs of oil leakage. Engine doesn’t smoke one bit either. Had another mechanic look @ it yesterday and he was suspecting blower. Will figure it out, just hope I don’t pay for a new engine by then
Tugger2
Senior Member
Looks like an American in your picture. What kind of work do you do with it?Im running 3 Americans ,4210,4450,5530 and a Lima75C these days . The Lima has a cummins which was slobbering badly after a 3 month crane job , but cleans up well after a week of bucket work, The 4/71 s in my Americans all slobber ,but cleanup after a couple of days of bucket work when i get it with them. The old 30 ton in my yard is the worst as it just idles a lot. If you keep good strong batteries ,cables, starters and a starter button up front in the cab, shut it off as much as possible while your standing by.
Bakelly78
Member
I have an American and two Link-belt 218A’s. Detroit is in the link-belt. Mainly set steel. Try to keep idle time down, but crane didn’t use to slobber this much. Lower has a Detroit and will idle all day with out slobbering...
Tugger2
Senior Member
I see your point.This might be too simple but has anybody has messed with your emergency shut down flapper recently?Ive seen them do funny things besides just killing the engine.
Tinkerer
Senior Member
Just curious if it started slobbering all at once or if it seemed to gradually get worse over time.
kshansen
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Not sure if anyone here has tried or heard of one solution to the slobbering of the 2-stroke Detroits.
I was told one time that for one used in lightly loaded application one, I won't call it a cure but a work around, was to install restriction plates in between the exhaust manifolds and the heads. Basically say an 1/8 inch thick steel plate with a bunch of small holes. Idea was to create a bit of back pressure to reduce the amount of "cooling air" from the blower going through the engine that was keeping the cylinders too cold.
Two problems I could see with this is first deciding how many and how big of holes to put in the restriction plates, guess it would be by trial and error. Second would be if you needed to get full power from the engine for a short time I could see it overfueling due to lack of air flow.
Wanted to try this on a small genset with a 3-53 that was used to keep a big genset warm nights and week-ends and never needed even 1/3 of it's rated output but could not get powers to be to agree to a test of the idea. Instead they decided to just stick in smaller injectors, believe we went from N45's down to N-35's. But that did nothing in my mind because the governor was already adjusting the fuel output to what was needed to maintain the RPMs. Injectors only limited the maximum flow. If I'm off base with that logic I'm open to correction.
If this idea would work I could picture an option of installing something like an exhaust brake in the exhaust where when max power was needed you could just flip a switch to open the butterfly to free up the flow.
I was told one time that for one used in lightly loaded application one, I won't call it a cure but a work around, was to install restriction plates in between the exhaust manifolds and the heads. Basically say an 1/8 inch thick steel plate with a bunch of small holes. Idea was to create a bit of back pressure to reduce the amount of "cooling air" from the blower going through the engine that was keeping the cylinders too cold.
Two problems I could see with this is first deciding how many and how big of holes to put in the restriction plates, guess it would be by trial and error. Second would be if you needed to get full power from the engine for a short time I could see it overfueling due to lack of air flow.
Wanted to try this on a small genset with a 3-53 that was used to keep a big genset warm nights and week-ends and never needed even 1/3 of it's rated output but could not get powers to be to agree to a test of the idea. Instead they decided to just stick in smaller injectors, believe we went from N45's down to N-35's. But that did nothing in my mind because the governor was already adjusting the fuel output to what was needed to maintain the RPMs. Injectors only limited the maximum flow. If I'm off base with that logic I'm open to correction.
If this idea would work I could picture an option of installing something like an exhaust brake in the exhaust where when max power was needed you could just flip a switch to open the butterfly to free up the flow.
Bakelly78
Member
Seemed to happen suddenly I think lol. It’s been that way for last two years and could run for another 10 that way I’m sure. Thought my operator said he had overheated engine, so I thought the head cracked and that was the cause. Had head redone and head was in decent shape when it came out. Checked blower real quick and dirty before I removed head, so thinking I need to check it thoroughly now...
DMiller
Senior Member
Suspect not going to find much if anything, these get to an age just cold slobber and nothing will stop it.
kshansen
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Well if it did overheat it may have damaged some rings or the pistons where you could not see with them still in cylinders.
I remember one 12V-71 we had that would run just great in a Haul truck once started, don't recall about the oil use on that one. Just needed a shot of go juice even on a 70ºF day. Finally at the end of the season it was brought in the shop and engine pulled. There was hardly any compression rings that were not broken! Started a bit better after new pistons and liners installed during overhaul!
RZucker
Senior Member
The exhaust brake idea makes good sense. A lot of the newer trucks do the same thing for warm-up. But would it work on the 2 strokes?
RZucker
Senior Member
On an inline engine, if the blower leaks it will puddle in the bottom of the housing after some idling time.
willie59
Administrator
Would it work on the two strokes? Good question. By design, the blower is both exhaust and intake. Piston top goes below the cylinder ports, exhaust valve opens, the blower forces out the exhaust gasses from the combustion chamber, and just before the piston top raises and closes the ports the exhaust valves closes allowing the blower to give the combustion chamber a charge of air for combustion. I'm just wondering if restricting the exhaust ports of the head would adversely affect this process.
RZucker
Senior Member
Thinking about it, I think it would tend to push condensed fuel right back through the cylinder ports into the air box. And condensed/unburnt fuel is the usual cause of slobbering.
old-iron-habit
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I did just that. It retired a bit over 5 years ago January 11th. Debby and I don't fish all the time. We hunt and travel as well.
I like money $!Money! LoL.