D17 leaking oil from spark plug
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=212243
Printed Date: 16 Sep 2026 at 1:04pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: D17 leaking oil from spark plug
Posted By: Putnamd17
Subject: D17 leaking oil from spark plug
Date Posted: 14 Sep 2026 at 9:24pm
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My d17 series 4 gas, has some oil leaking from the spark plug closest to the fuel tank, I checked the compression and it was about 157, there is some smoke coming from the exhaust as well, I am thinking this is a valve seal issue. Anyone run into a similar problem before?
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Replies:
Posted By: DrAllis
Date Posted: 14 Sep 2026 at 9:31pm
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There are no valve seals or valve stem umbrellas. The valve guides and valve stems are probably worn out. The piston ring grooves are loose top to bottom, the sleeves have a heavy ring edge at the top and the ring gaps are too wide. In short, everything wears out at the same time. A 98% chance it is time for an overhaul.
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Posted By: DrAllis
Date Posted: 15 Sep 2026 at 6:21am
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How do you use or intend to use the tractor?? As long as you aren't fouling a spark plug all the time, you could run it for a long time with this condition, using it for light jobs/short run times. If you intend to grind feed weekly and expect to operate it mowing, raking and baling hay, then your days are probably numbered.
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Posted By: Putnamd17
Date Posted: 15 Sep 2026 at 6:41am
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I was hoping to use it for some light plowing with a 2 bottom and bailing about 5 acres of hay.
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Posted By: Putnamd17
Date Posted: 15 Sep 2026 at 6:42am
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I had a mechanic go through the engine and look over everything he said he wouldn’t be concerned with anything at the time he went through I asked him about my cylinders and he said they had a lot of life left yet.
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Posted By: DrAllis
Date Posted: 15 Sep 2026 at 11:06am
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"Go thru the engine"..?? what does that mean exactly ??? He had it apart and looked at the cylinders?? and now it smokes blue out the exhaust ??
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Posted By: DrAllis
Date Posted: 15 Sep 2026 at 11:08am
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Your oil leak isn't as simple as a valve cover gasket leaking ?????????
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Posted By: Putnamd17
Date Posted: 15 Sep 2026 at 12:29pm
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I do not see any oil coming from the valve cover, he went through and mainly replaced all the seals and such said the cylinders looked good he had the engine out and completely apart on an engine stand, I do not see much blue smoke there was some white smoke but only for a little bit
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Posted By: Dirt Farmer
Date Posted: 15 Sep 2026 at 12:40pm
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What are the chances that the crush washer is missing on the spark plug and what you are seeing is seeping past the threads
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Posted By: DrAllis
Date Posted: 15 Sep 2026 at 1:16pm
A fairly typical result of an "oil burning" AC engine is engine oil leakage around a spark plug. That's just a fact on these engines. So, does it use oil or not?? and you just bought the tractor so you don't really know ?? If he didn't have the cylinder head removed, he only saw the cylinders from the bottom side, which is kind of meaningless.
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Posted By: Putnamd17
Date Posted: 15 Sep 2026 at 1:38pm
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I know he had the head removed, it uses some oil but there is a small rear main leak so I’m not sure where most of it goes but it seems like I’m loosing more oil than what’s coming out of the rear main. It is not a very large leak, it has a new head gasket should I be running different spark plugs in it? Hotter ones? It has the 3/4 ones recommended in the book in it
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Posted By: DrAllis
Date Posted: 15 Sep 2026 at 2:14pm
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If you aren't fouling a spark plug, there is zero reason to go to a hotter heat range plug.
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Posted By: Putnamd17
Date Posted: 15 Sep 2026 at 2:22pm
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The spark plug is completely covered in carbon very black.
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Posted By: 8070nc
Date Posted: 15 Sep 2026 at 4:33pm
Id put a new set of plugs in it and run it some and see what happens and figure it out from there
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1984 80780
1957 D14
DES 300 with 25000 engine
616 tractor
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Posted By: DrAllis
Date Posted: 15 Sep 2026 at 6:45pm
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It's sad to think that he had the engine out and in a stand?? and the rear seal wasn't replaced?? or he replaced it and it still leaks?? Could be either one......
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Posted By: Putnamd17
Date Posted: 15 Sep 2026 at 7:42pm
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It was replaced and still leaks which is why I’m questioning the rest of the engine
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Posted By: DrAllis
Date Posted: 15 Sep 2026 at 8:35pm
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He doesn't know how to install a D-17 gas rear seal correctly. You haven't said how long you've owned this tractor.
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Posted By: Putnamd17
Date Posted: 16 Sep 2026 at 4:14am
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Maybe 2 years but the first year it sat around didn’t work at all only was ran to move it, and he just went through the engine a few months ago so was hoping to start using it
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Posted By: Putnamd17
Date Posted: 16 Sep 2026 at 4:15am
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Work as in pull anything only moved from on shed to another
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Posted By: DrAllis
Date Posted: 16 Sep 2026 at 5:49am
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He had to remove and reinstall the oil pan to do the rear crankshaft seal. If one isn't proficient at those tasks with this engine, it could be leaking at either or both areas.
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