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Discussion Starter · #1 ·
Has anyone ever heard of a plugged muffler causing slobbering in a diesel? I wrote into this column 9/2008 about this slobbering issue. Since then the engine has been rebuilt, the injection pump has been rebuilt, and new injectors installed and the slobbering continues! Compression check was OK!

The mechanic said that he put a good load on the tractor before I brought it home and that lots of "junk" came out of the muffler-it burned the paint off the outside of the muffler. He said that he had the tractor at idle for some time without the muffler and that there was no issue. I just brought it home to cut some wood so it idles off and on while pulling in the twitch of wood, etc although I am shutting it off more now to avoid long periods of idling. No slobbering while pulling a 3 bottom plow, lime spreader, or disk.

Could a broken baffle inside the muffler cause something like this to occur? I don't know where to turn now and neither does the mechanic!
 

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I doubt a broke baffle would cause this but excessive idle, or an engine that does not have the piston rings properly broken in and seated could cause this problem.

When the engine is run hard under a substantial load, the EGT's in each cylinder are substantially higher for a sustained period of time which burns off the "slobber" or partically combusted fuel and oil residue.

I would suggest hooking the tractor up to an attactment or impliment such as a generator or hay bailer and let the engine get a good hard run in and then check to see if you are still having these issues.

My Cummins engines will do this to a certain degree with short trips or local driving with no load. On long trips or pulling a heavy load, they clean right up and the blow by is substantially reduced.

Another thing that can substanitally contribute to this problem is a thermostate the is set to open at too low a temperature, a stuck thermostat, or no thermostat. Up to a point, diesels like to be run at the upper end of the temperature range in the 190 to 200 degree range. Some with the proper mods even higher. Too low an operating temp and the combustion cycle occurs poorly and in incomplete not to mention that the engine oil gets fouled quickly.
 

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Discussion Starter · #3 ·
A load was put on this engine and that is when the "burnoff" in the muffler occurred. I have put on more than 50 hours on this tractor since the re-build. I pulled an 8' bush hog for about 40 hours at full throttle. How long can it take to seat those rings?

The thermostat was replaced and cooling system flushed/replaced. The temp gauge comes up to where it normally does-between the 1st two marks.

I have reduced idling time to nearly none at all, not that it was idled much anyway. I put several hundred hours on this tractor before this mess first surfaced. I guess I'm just going to run it, can't afford to dump any more money into it.
 

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Each engine manufacturer has different information but at one time Cummins stated that the 5.9 Cummins break in period was between 5000 and 20,000 miles. A lot depends upon the sustained load you put on the engine.
 

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Discussion Starter · #6 ·
"fuel injectors bend tests for pop pressure, spray pattern, and leakage?"

Not sure about these tests. The injectors were the last parts installed and the mechanic said that they were all running within 100 lbs of 3600 psi.

I hooked onto my 14' disk this afternoon after I put two large cement blocks on the back of it and pulled that in 4th gear. That dried things in short order and burned all of the slobber off of it! According to the temp gauge, it warmed up and ran as it should.
 

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The only engines I've seen that have slobbered oil, not fuel, have been JDs with Yanmar engines. In every instance, there has been a broken piston, between the rings, and ring(s) on the back cylinder.

I think you're referring to fuel being slobbered, which evidently is totally unrelated to thermostats, rings, injectors and pumps. Since it was slobbering prior to replacing all of those items and it's still doing it, they must have not been the problem.

A restricted exhaust could cause some fuel mix problems in a direct injection engine, but the air flow would be just as, or more so, restricted/choked at higher rpms as it would at low rpms.

In colder weather, as if I know anything about cold weather here in Texas, it may be necessary to restrict the air flow through the radiator to get up to the proper operating temperature. I think that could be a practice on 18 wheelers.
 

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Discussion Starter · #8 ·
I did run a canvas over the radiator to block the air flow last fall, but it didn't seem to matter much. It's an intermittant issue and usually occurs when the tractor is not working hard (enough?). I do not let it sit and idle at all. This whole thing occurred right after I flushed the radiator out back in 2008. Thousands of dollars later, we've not really gained a thing with all of the repairs, although I think that the fuel economy is better.
 

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It's beginning to sound like the rich fuel mixture isn't burning out of the exhaust in low load situations. After the rpms and load get up, there's enough exhaust heat to cook off the residue.

What have you done with the air intake portion, i.e. filter and etc.?
 

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I am going with TF on the tstat, sounds like low combustion temps, before you spend $$$$ more, you should spend a few $ on a tstat. Nothing ventured nothing gained.
 

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Talked with my neighbor today, who said he had a 674 at one time that did the same thing. In that case, it was valve stem seals installed upside down, i.e. cup up instead of down, after a rebuild.

I've never been into an English tractor motor, but I know there are many styles of valve stem seals. Anything from a simple "O" ring to metal with rubber insides. The oil pressure from the rocker arms can and will leak past the intake valves, but rarely past the exhaust valves (they have pressure on them when the valve is open and the intake has a vacuum when it's open).

There are a couple of ways to replace the seals without taking the head off. 1) use air pressure through the injector port to hold the valve closed, or 2) put the piston on TDC, so the valve can't fall in very deep. There's a spring compressor built for head on seal replacement that grabs the spring close to the head and compresses the spring retainer. The stem keepers can be removed then, which allows access to the seal.

Prior to doing all of that, take the valve cover off and look between the spring windings and see if the seal is on right. If you're like me, you'll need a flashlight to see anything.

Oil leaking past the seals won't show up very much on the dip stick, but it also doesn't burn as good as diesel does.

Checking the air flow is as simple as removing the filter and see if it still slobbers.
 

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Discussion Starter · #13 ·
The mechanic replaced the thermostat during the rebuild-I'm sure it's the right one, but of course not sure if it's working properly. I think that he restricted the flow slightly too to ensure that the temp came up. The temp gauge comes up right between the first 2 marks like it always did before (pre-slobber). But anyhow, what is the correct thermostat for this engine (D312)? How long should it take for this engine to heat up in 50 or 60 degree weather?

Haven't done anything with the intake, just replaced the air filter during the rebuild too.

I don't think it would be the valve seals....at least I would like to think that they were properly installed. I will watch and see what the oil consumption is like though.

I hooked on to my 14' disk Saturday and burned over 3/4's of a tank of fuel pulling it. I have well over 500 lbs of weight on it so it digs deeply; I lost traction several times during the first time over the field (fresh after moldboard plowing) so it pulls hard. Slobber burned off after 10-15 mins and everything dried up. It's still dry today after pushing some dirt around and bucketing some wood, so maybe the rings have seated finally and the problem is resolved.
 

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Discussion Starter · #14 ·
Huh, so much for relying upon mechanics! (oh, I guess everyone makes mistakes). I pulled the thermostat out yesterday and found it to be a 180 degree thermostat instead of the 190 called for. Put it in and the temp gauge is right back where it always was! I won't guarantee that it won't slobber again, but it's gotta be better than it was. Thanks for the advice.
 

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Talked with my neighbor today, who said he had a 674 at one time that did the same thing. In that case, it was valve stem seals installed upside down, i.e. cup up instead of down, after a rebuild.

I've never been into an English tractor motor, but I know there are many styles of valve stem seals. Anything from a simple "O" ring to metal with rubber insides. The oil pressure from the rocker arms can and will leak past the intake valves, but rarely past the exhaust valves (they have pressure on them when the valve is open and the intake has a vacuum when it's open).

There are a couple of ways to replace the seals without taking the head off. 1) use air pressure through the injector port to hold the valve closed, or 2) put the piston on TDC, so the valve can't fall in very deep. There's a spring compressor built for head on seal replacement that grabs the spring close to the head and compresses the spring retainer. The stem keepers can be removed then, which allows access to the seal.

Prior to doing all of that, take the valve cover off and look between the spring windings and see if the seal is on right. If you're like me, you'll need a flashlight to see anything.

Oil leaking past the seals won't show up very much on the dip stick, but it also doesn't burn as good as diesel does.

Checking the air flow is as simple as removing the filter and see if it still slobbers.
Thank you for this! To confirm, if I get the piston to TDC, the valve won't fall far enough that I can't pinch the end of it and pull it back up? I'm not sure how to pressurize the cylinder through the injector port as there is no thread on the wet liner in which to screw the air hose onto (I've read need at least 80psi to keep the valve from falling in the head).
For my purposes, I have an IH 574 diesel. I'm blowing a plume of blue smoke on start up which leads me to believe I have oil making its way into cylinder from valves.
 

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That's pretty much normal for your tractor to belch out blueish, black smoke at start up. Its because the cable you use to shut it down is also for start up. In the start position it puts the injection pump in a very rich fuel position for easier start, kinda like a gas engine using the choke. After start up you move the cable to the run position and then it will clean up and idle fine
 
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