99 Sportsman 335 oil leak - Polaris ATV Forum
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post #1 of 11 (permalink) Old 07-15-2019, 07:04 PM Thread Starter
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99 Sportsman 335 oil leak

I have a 99 Sportsman 335 A99CH33AA that I am doing some preventative and age related maintenance to and I have a new oil leak that puzzles me.
First question, what is behind this access cover?
I don't want to shoot myself in the foot by opening a Pandora's Box when I don't really know what goes on behind the cover plate.


The reason I ask is the machine is leaking oil from the hole the screwdriver tip is pointing out.
It spits a small amount of oil while running and perhaps a half dozen or so drops of oil will drool out from this hole after engine shut down.


I have looked at the various parts breakdowns for this area and I don't get a lot of information aside from there appearing to be a bearing and oil seal in that area.
Why is there a hole there?
Is there supposed to be something in that hole?
Is it as simple as opening the cover, replacing the oil seal and closing the cover again to get it to stop leaking?
Thoughts on why it suddenly started leaking?

Looking forward to the group's input.
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post #2 of 11 (permalink) Old 07-16-2019, 05:10 AM
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That cover is where the water pump would mount on the liquid cooled version of the engine. Behind that cover is the end of the balance shaft and an oil seal. The seal is leaking oil and the hole is the weep hole that would allow either oil or coolant to drain out of depending on which seal was leaking on the liquid cooled version. Since your engine does not have a water pump, the counter balance shaft seal is leaking oil and the oil escapes from that hole. The cover plate does not have a gasket, so plugging the weep hole will just delay the eventual leak will come from the cover. You just need to replace the shaft seal.

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post #3 of 11 (permalink) Old 07-16-2019, 08:52 AM
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Quote:
Originally Posted by latebird View Post
That cover is where the water pump would mount on the liquid cooled version of the engine. Behind that cover is the end of the balance shaft and an oil seal. The seal is leaking oil and the hole is the weep hole that would allow either oil or coolant to drain out of depending on which seal was leaking on the liquid cooled version. Since your engine does not have a water pump, the counter balance shaft seal is leaking oil and the oil escapes from that hole. The cover plate does not have a gasket, so plugging the weep hole will just delay the eventual leak will come from the cover. You just need to replace the shaft seal.
Yeah, its the counter balance shaft seal leaking. Number 22 in the pic. I don't know if it can be replaced with the shaft still in there though. I think you'd have to split the cases?
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post #4 of 11 (permalink) Old 07-16-2019, 12:02 PM Thread Starter
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Thanks for info.
That oil seal is what I was thinking.
Anybody have a definitive thought on if the case needs to be split?
Since I don't have the seal in my hand I can't guess and I am away from the machine for a few days so I can't open it up and look to see if I can pull it.

Thanks again for the input.
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post #5 of 11 (permalink) Old 07-16-2019, 03:39 PM
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Generally when the parts breakdown shows the seal on the outside of the case, it can be gotten out and installed without splitting the cases - just have to eyeball it and make the call

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post #6 of 11 (permalink) Old 07-16-2019, 05:02 PM
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On a second look, you may be correct latebird. The image does show the bearing coming from the inside while the seal is from the outside.
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post #7 of 11 (permalink) Old 07-16-2019, 06:12 PM
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I did say generally - there are exceptions

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post #8 of 11 (permalink) Old 07-22-2019, 02:48 PM Thread Starter
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Thank you both for the input. I ordered an oil seal last week before I left town and it should be here today or tomorrow.
I pulled that cover plate off and this is exactly as I found it.


Well there's your problem.
The next question is, why did it eject the oil seal. Thinking it might be excessive crank case pressure I checked the breather line to the air box and it appeared to be free so who knows. Anybody heard of those oil seals just falling out after 20 years?
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post #9 of 11 (permalink) Old 07-23-2019, 04:40 AM
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Yes - seals will occasionally 'extrude' themselves due to expansion and contraction. It can be caused by internal pressure, bad bearings, vibration, defective parts, poor workmanship and improper installation to name a few reasons.

Sometimes the old seal can be reinstalled and work perfectly. If you have a new seal, you may as well put it in, but if the original seal appears undamaged, you might put it in the package the new one came in and keep it as an emergency replacement spare.

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post #10 of 11 (permalink) Old 07-23-2019, 06:58 AM
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Quote:
Originally Posted by latebird View Post
Yes - seals will occasionally 'extrude' themselves due to expansion and contraction. It can be caused by internal pressure, bad bearings, vibration, defective parts, poor workmanship and improper installation to name a few reasons.

Sometimes the old seal can be reinstalled and work perfectly. If you have a new seal, you may as well put it in, but if the original seal appears undamaged, you might put it in the package the new one came in and keep it as an emergency replacement spare.
I was gonna ask if there is any play in the bearing/shaft OP?
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