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Hey all I have run into a problem with 3 different Polaris Rangers with oil leaks at the oil filter. I have checked for debri on the sealing surface, there is no gasket or o-ring material on the sealing surface and it only happens after 20 hours of use. I have tighten the filter using an oil filter wrench but at around 20 hours it leaks again. I am told that the 800 cc engine had some oil pump pressure relief valves will stick, causing seal failure. Anyone have any input on this and what is the fix?
 

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The problem is usually caused by dirty oil, but the consensus among Polaris affectionado's is that the pressure relief plunger (an 8 mm x 16 mm dowel pin) which is steel in an aluminum bore is is galling the aluminum and sticking open or closed.

If the valve sticks closed oil pressure is uncontrolled and will exceed 100 psi at 6000 rpm. The degree of stiction may be related not only to the cleanliness of the oil, but also to the heat of the engine and clearance between parts. The high pressure can be great enough to force oil past the oil filter seal and in some cases rupture the oil filter can. It can also cause valve float and temporary loss of compression.

If it sticks open, oil pressure can be as little as zero at idle which may not cause engine damage, but can attribute to lifter rattle and rough or no idle. An engine idling for an extended period (more than a minute) with less than 4 PSI of oil pressure may experience galled cam lobes and dished lifters prior to engine failure.

There are several opinions as to the 'FIX', but each one is just a Band-Aid and while may be a very good Band-Aid, does nothing to address the root problem.

The first Band-Aid is to change the oil at more frequent intervals than recommended by the manufacturer or happens to be the habit of the owner. Polaris recommends changing the oil every 100 hours, 12 months or 1000 miles, but more frequently for severe use. Mudding, snow plowing and extended periods of idling are examples of severe use.

Another band-aid is to polish the dowel to reduce it's diameter about .001 to 002." to increase the clearance in the bore which alleviates binding due to heat.

Another band-aid is to replace the dowel with 2 - 8 mm diameter steel bearing balls - they are fractionally smaller, have less surface contact between the parts and are harder than the dowel.

The fix would be to sleeve the pressure relief bore with stainless steel which would retain it's internal dimension more closely than the aluminum of the engine case when hot or to replace the individual parts with a cartridge relief valve. Both would require the engine be completely dismantled and taken to a machine shop for modification or it should be addressed by Polaris at the engine design level.

There are a couple of videos on You Tube - just search for Polaris 700/800 oil pressure relief fix
 
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