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So I have a 1990 JD 318 with the 50" mower deck. Love it. I am new to working on small engines, but learning. This past week I changed the oil and filter.

When I filled it back up with oil, I filled it slightly above the full line on the dipstick. I let some oil out till the oil came right down to the line. Then I twisted the dipstick on and got busy with other stuff.

So then today I was mowing the lawn, and after about a half hour of mowing and all of the sudden it coughed a couple times and a bunch of blue (maybe white) smoke came out of the exhaust. Like two big puffs of it. Yikes! It coughed and ran rough for about 5sec and then it went back to running fine, with no smoke or anything.

I freaked out and promptly killed the blades, lifted the deck and took it straight back to the garage. When I got there I turned it off and opened the hood. I noticed that the dipstick was not screwed down into it’s pipe. it was unscrewed and up about a half inch. (but no oil had come out or sprayed or anything - it was dry all around.

Then I took the air filter off and it and the foam pre-cleaner around it were saturated with oil. Oil coated the inside of the air filter box.
170820-oilinfilterbox.jpg

You can see the remnants of the oil all around in there, after I had wiped most of it up. I threw out the pre-cleaner and the air filter and will get new ones tomorrow. I also wiped out all of the oil you see here, as well as took off the little plate there over the carburator and cleaned both sides of it.

After I cooled the engine I checked the oil level, and it’s now half way between full and empty.
170820-oillevel.jpg

So my questions are: Did I wreck something? What happened? How did the oil get inside the air filter box? Do I need to pull the engine or something?

I am new to doing work on small engines, but will eventually be restoring this 318, so I have no problem getting my hands dirty working on it. My guess after thinking about it a bit is that even though the oil level was just about at the full line, when it got hot something happened to somehow push oil into the cylinders. That's about as much as I have reasoned out. I just need to know what happened and how to fix it and how to make sure it doesn't happen again...

Thanks!
 

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Hi, the oil in the breather box is from the crankcase breather getting oil pushed through it due to the higher level. You shouldn't have caused any damage to the engine, just be careful when refilling it next time. The smoke was probably caused by the air vacuum via the carburetor, sucked the excess oil in through the air intake, resulting in the puff of smoke. I would say just wipe up the extra oil in the box, let the tractor sit for a few hours and recheck the oil level.

Also keep in mind, in a pressure lubricated engine, the level will always appear higher after you drain and refill with clean oil as the engine needs to run to fill the oil pump, filter, and all the oil passages.
 

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The oil came from the crankcase breather due to the loose dipstick. The engine will be fine, just make sure the o-ring on the dipstick is good and seals to the top of the tube.

I've has this same thing happen to me.
 
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