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Blowing oil on a Kohler Magnum 18 Help

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Jeffie
Join Date: Jul 2003
Posts: 17 NJ, 07092
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2003-05-25          55553

After not using my Cadet for a couple of months, I started it up to move an empty car trailer. Under load the motor smoked and died. This is a low hour rebuilt, 200hrs. The motor was pumping oil up through the breather tube into the carb. I began to tear it down and discovered 5 dead mice and a nest in one side of the engine, between the cooling fins and sheet metal. Valves, cylinders, rings, all look like new. Any ideas as to what would cause such a buildup of pressure to push oil out of the crank like that? Cylinders still have cross hatch on them. Could overheating cause it? Should I just buy new gaskets and put it back together. I only have one good arm, so I hate to do this job twice. Any advice would be greatly appreciated.

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Blowing oil on a Kohler Magnum 18 Help

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-05-26          55574

That's a tough call. Too bad it happened. I guess in tearing it down you noticed if the oil level was normal, if the engine binds and if it had normal compression. If those were OK and the rings still rotate in their grooves putting it back together may be about the only way to figure out what was wrong.

The usual explanation for oil blowing out the vent, or in this case it sounds like the engine has a closed crank ventilation system, is excessive blow-by or high oil levels. I'm not sure that over-heating in itself would cause excessive blow-by unless some obvious damage can be found. I would check for stuck or broken rings. I also don't know if a recent rebuild that was left sit awhile might end up with stuck rings but that seems a stretch.

Occasionally you hear of an engine with stacked rings that will have a lot of blow-by. Stacking occurs if the ring end-gaps line up, but that's usually before the engine warms up. The gaps disappear in an engine at normal operating temperature due to expansion. I guess rings in an over-heated engine might become distorted and that could cause blow-by in some engines. I wonder how long the engine operated before it stalled. Maybe there'll be a comment from somebody who knows the engine.
....

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Blowing oil on a Kohler Magnum 18 Help

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2003-05-26          55577

Jeffie, you don't say what parts were replaced in the rebuild, but I will assume it was just the usual 'freshen up' type rebuild.

This being the case, and given that the machine has sat for several months, I would put my money on stuck rings. We get this fairly commonly with the 18 Mag's we have in our older Ferris front-mounts, a little rislone or Marvel Mystery oil helps, but doesn't prevent it totally.

If everything looked good on the teardown, then there is only so many things that could cause the symptoms you describe, the rings being most likely of the culprits.

Best of luck. ....

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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2003-05-26          55578

I would think Murf knows best. For a little more assurance I would micrometer the cylinder bore to check if the possible asymetical over heating did not put it out of round.
Peters ....

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Jeffie
Join Date: Jul 2003
Posts: 17 NJ, 07092
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2003-05-26          55614

Thanks everyone for your input. I will borrow a Mic and check the cylinders. The rings didn't,don't appear to be stuck. Everything inside looks like new. To make matters worse, I only use synthetic or synthetic blend. I have had nothing but good experience with synthetic oil. I am hoping the rings were the problem, but in my gut I don't see how, unless they became unstuck when I disassembled it. The rebuild looks to be very complete. I guess I should take the rods off and replace the rod bearings since I have it down this far.

Ido have a brand new 20hp Command series butit has the short snout on the crank, wouldn't be able to put my PTO on. Ahh me, life is difficult some times. ....

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2003-05-26          55616

Jeffie, two little tidbits of info I don't have might help me to make a guess-timate.

First, I don't know what the weather was like there in 'Joisey', if it was really warm, the amount of extra heat required to cause an overheat might not be very much, the mouse nest might be enough, on the other hand if it was a cold day, the amount of work to cause the overheating from work alone would be significant.

Secondly, you didn't state, was the smoke coming from the exhaust, or just coming from the engine generally. If the smoke was coming from the exhaust I wouldn't be so concerned since any burning oil would cause smoke, this alone doesn't indicate damage.

It's not possible that the engine was just overfull with oil was it? It sure would explain the situation.

Best of luck. ....

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Jeffie
Join Date: Jul 2003
Posts: 17 NJ, 07092
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2003-05-26          55621

Thanks, Murph. It was a mild day, maybe 65. Tractor ran fine for about twenty minutes, first at idle then full throttle for a few minutes, no problem. It was when I had it under load pulled the trailer about twenty feet that it smoked like nuts through exhaust, and stalled the motor. I changed the oil and filter, tried it again, same thing. I believe I had the correct amount of oil in it. When I took off the air cleaner the oil was shooting up into carb through that vent hose. It was perking up like a coffee pot does. The mouse nest was built out of seat filling, a wool like material, and really packed in there. The dead mice looked old however.(Cooked it's hard to tell)One thing, it appeared the oil had a lot of gas in it, maybe due to the misfiring? ....

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2003-05-26          55627

Ahh, now we're getting somewhere, it definitely sounds like a ring problem now.

The gas was unburnt fuel that got pushed past the ring and into the crankcase instead of compressing and being ignited in the cylinder. This in turn caused oil, which is splashing around in the crankcase to 'perculate' up the PCV tube with every blast of air from the cylinder. In a case like this overheating is normal.

Now all you have to do is figure out what happened to the rings in that cylinder. If it's any consolation, I don't think the mouse nest was part of the problem, it was only a coincedence that you discovered it while searching for a casue of the main problem.

Best of luck. ....

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Jeffie
Join Date: Jul 2003
Posts: 17 NJ, 07092
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2003-05-26          55629

The rings are free and clear now. Or appear to be. Should I just reassemble or should I replace?

Thanks for your help, BTW. I am one armed and it takes me longer to do things. My bad arm is crushed and all pinned up, pretty useless. So I appreciate direction. ....

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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2003-05-26          55639

Jeffie;

Ok, I would check for out of round, but with the new info I would suspect that after the rebuild the rings did not seat. A lot of manufactures do not recommend synthetic oil during the breakin period. The synthetic is too slippery to allow the rings to lap and seat properly.

Peters ....

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Chief
Join Date: Jul 2003
Posts: 4297 Southwest MiddleTennessee
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2003-05-26          55650

Jeffie, I would suggest using a break-in oil in that engine for at least the first 10 or 20 hours. You can buy it at the local John Deere dealer. They require this oil to be used in nearly all of their engines to get a good ring and general engine break in. You can go to synthetic after the break in. Concur with what Murf said abouve. Good luck with the trouble shooting and getting that baby to run right. ....

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Jeffie
Join Date: Jul 2003
Posts: 17 NJ, 07092
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2003-05-26          55661

I think the engine is well broken in, it has 200 hours on it and I have not had a problem before. ....

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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2003-05-26          55662

Jeffie;
You really know how to blow holes in a great theory. I guess you are back to checking the cylinder bore and assembling.
I have seen problems with dirt in the cooling fins on the old MX dirt bikes. Some time they returned to round after they cooled.
Peters ....

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-05-27          55693

I don't know if this engine has a gravity fed fuel system and if so whether there's a fuel cut-off valve that's used and also if it used a diaphragm carb. It would be handy to know how the tractor acted when it killed and how long it ran before killing. I'm tying to figure if it killed because it overheated or because oil fouled the plugs.

I know my old riding mower with a 12HP B&S has a gravity system. If runs out of fuel the float bowl can stick and then fuel drains into the carb throat. It'd be good to know if the engine was an oil burner during its 200 hours operation since the rebuild. Some fuel ends up on the ground but I imagine some ends up in the crankcase as well. If the oil were highly diluted with gas I'd think something like my mower's problem might be the problem here too.

If the pistons will be miced, I'd work from a specs table. Not all pistons are round when they are cold. Some are engineered to come into round at operating temperature and you can't tell if they're within tolerance without a specs table. I'd also check the cylinder bores. A bunch of things can happen in rebuilds. Aggressive cylinder honing combined with old pistons can put the clearances out of tolerance. Most piston and cylinder sleeves come in standard and over-sizes. Sometimes the wrong sizes are used or machining needed to actually accommodate an oversized part is skipped.
....

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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2003-05-27          55710

I know that Murf's area is a little cooler but I think 20 minutes of running on any engine with restricted cooling can cause a problem. You might be okay just to clear it and go on. ....

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