Sunday, January 9, 2011

Polaris Sportsman 500 ATV

I have my own vehicle in the shop today, a 2008 Polaris Sportsman ATV.  My wife was driving it a few weeks ago and she called me and said "something exploded, there is oil everywhere!"  This first photo shows what I found when I went to get her.  The oil reservoir had actually exploded.

These Polaris ATVs have a 4 stroke engine with a dry sump oil system.  Unlike a typical engine with an oil pan or sump on the bottom of the engine, these engine have a separate reservoir to hold the oil.  This allows the engine to be more compact and probably makes it easier to increase the ground clearance under the engine.  I think that it also helps with cooling the engine,  the oil reservoir has a large surface area to dissipate the heat in the oil. (There are probably more reasons than this to use a dry sump, but these seem like the obvious ones.)

I have seen this problem several times before on other peoples machines.  ATVs in the village make a lot of short trips in cold weather.  They do not get run long enough or hard enough for the oil to heat up.  This allows moisture to build up in the oil and the vent line on the reservoir gets plugged with frost and ice.  Once the vent is plugged the pressure builds up and blows the side of the tank off.  Polaris is aware of the problem and has tried to prevent this by putting a small slit in the vent line.  This slit in the rubber hose is supposed to stay closed during normal operation and open up if pressure builds in the line.  Unfortunately it seems like the blockage happens right at the tank and the pressure can not be relieved. 

Another potential problem with the moisture build up is the possibility of ice forming in the bottom of the tank when the vehicle is parked in the cold.  If enough ice forms it can block off the oil supply line to the engine.  This of coarse leads to an oil starved engine and all kinds of problems if the operator is not aware of the situation.

This photo shows the new tank and the original.  It is interesting how the whole side of the tank exploded.  This is the same way that I have seen other ones fail.  I am surprised that the tank doesn't simply split open?

To try and avoid future problems I have decided to insulate the tank to help the oil heat up better in cold weather. 

I cut up an old camping type sleep pad to cover the sides.  I am using DOW 732 silicone to glue the closed cell foam to the tank.  732 is great stuff, I use it for everything.

 Here is the completed tank ready to install. 


  1. The problem with insulation is that it will hold the oil temp longer after shut down, it will do very little to help warm up the oil on short trips. If you have enough short trips in a day this may hold the heat from the first so that it slowly warms up each time and may get to operating temp over the course of the day.

    Is it possible to put an oil / water seperator in the lines between the the engien and the tank? That might be a visible reminder (if it's not buried in the machine) and could be heated and drained periodically.

  2. I think the insulation will help on short trips. There is a large volume of oil passing through the tank, the tank acts like an oil cooler. Insulating it will help raise the oil temp right away.

  3. Hey nice tip. what oil that u used? im wondering which oil product is best for my polaris actually

  4. Jeorgey,
    I do not think that any particular brand of oil is best. Your Polaris dealer would tell you to use Polaris oil, but there is no reason you have to. You should of coarse follow the manufacturers recomendation on what weight (5w-30, 10-40, etc) to use.

    There are two main options when picking oil, synthetic or mineral. The synthetic oil is going to be much thinner in cold weather. Put a bottle of mineral oil and one of synthetic in your freezer over night. The next day try pouring each one and you will see the differance right away. The thinner oil (synthetic) will work better during start up when your engine is cold.

    For recreational vehicles that do not get lots of use I think spending the money on synthetic is the way to go. Any of the major brands (including Polaris) will work fine.

  5. I didn't want this to happen on my 08 6x6 with 3600 miles on it. I put an old style aluminum tank on it, with 2 kats 25 watt heater pads (100*-110*) on there. I had put a caul plate on my plastic tank with an old oil sump tanis heater but the wires are to fragile to last but only one winter. I am worried if any tanis/kats heater pad shorts, I'll wake up to a puddle of oil if it melted through my tank. Along with an arctic cat inline "temper-mental" coolant heater on my lower hose, when the coolant heater works, it will crank all winter with no problem what so ever with only being plugged in for an hour. When the coolant heater doesn't kick on I just leave it plugged in over night. Easier to keep the oil warm than try to warm a cold soaked engine. I'm in Nome, and usually change my oil when I get moisture in it rather than time limit. I change my oil more in the winter than summer, due to the moisture. I notice with the aluminum tank and 2 kats heaters, the moisture content in a month has been zero. I use 5w-20 castrol syn. Polaris told me that their oil was 5w-50, but still at -40*, nothing seems to flow to my liking.

  6. Where did you get the aluminium tank from?

    The syn oil flows a lot better in the cold, it helps with starting.

    If the engine gets run hard enough it will heat the oil up enough to drive the moisture out. Unfortunatley driving around town does not work the machine hard enough to heat it up. Your electric heaters will give you a head start on heating it up. Sounds like a good solution.


  7. This just Happened Today to My friends Polaris Sportsman 500 2up. exacty identical. I'm glad I found your Blog. Someone else was driving his atv as well. What are the chances that no oil is left in the engine and it all drained out while riding it? Should;nt the OIl/check engine light come on?

  8. How long was the engine running after the tank blew up? As long as the engine was turned off quickly (a minute or two) there should not be any engine damage.

    If the engine was run for too long without oil there will be problems. The valve train and the piston could both be damaged. The cam could wear down (this would be cause a clicking sound when the engine runs). The piston could also be scored (scratched) or ultimatly become stuck in the cylinder.

    The tank costs about $130 and only takes an hour to replace. After fixing the broken tank start it up and listen to the engine and look for smoke in the exhaust. Let me know how it works out.


  9. I got an old aluminum tank off ebay, $45 with shipping. Just search polaris sportsman oil tank. There are always several on there. I would buy 3 of these before I would buy anything from Morgans. All the bolt patterns are the same, and the oil quantity is the same. The pickups are identical, and the only pain in the rear is the filling of the oil tank, because the fender isn't cut out for the fill(will be modified with a hole saw so I can get a long neck funnel in there. I used a cut soda bottle to fill the tank. I think mine was off a 96/97 325 or something else. It came with the old hoses, and also a bypass valve in it. The banjo lines off the old tank are different sizes that what are on there now. I didn't put the bypass valve in my system yet. It would bypass the tank if the tank pickup was frozen and when it thawed would then pick up the oil out of the tank. I had to switch my fittings coming off my crankcase because of the line sizes, but it wasn't a big issue. I want to replace the lines with new so they aren't old and have the memory in them from the old machine that they came off of. Right now, everything is still just too cold to crank, because my arctic cat atv heater isn't working currently, such a waste of money that was. Trying to figure out a kats block circulator system with check valves so I can put it in my front(almost useless) rack and not have the heater lose prime.

  10. I ceased my 500 up, and all I had to do was replace the piston and cylinder. It gaulled the cylinder, but to this day I have still not been able to fix the oil leak on the banjo lines from the crankcase to the head/cyliner. I bought new from Hatchers Pass Polaris and they mailed it up here for me It was around $650 for everything I needed. I didn't even try local here because of a bad experience with them.

    There is no low oil psi light/cut out switch on sportsmans. Search online there is a port beside the exhaust where you can pipe in a oil psi switch and make a idiot light on your pod. I don't have a straight answer for the PSI, but a volkswagon bug has a 3-7psi switch for their low oil psi. For me, that low of oil psi is enough of a warning for me and that is better than nothing. I don't care about low oil psi at startup or idle, but when riding it shouldn't be that low. I think one place I read it was like 5 to 7 at cold start up, then 10 to 15 psi at half throttle and 15-20/25 psi for full throttle. I am also going to tap my thermostat housing, and put in a manual probe. There are small water temp, full swing gauges that will fit right below your spedo display and fit on the pod. I am thinking about getting a dual oil psi/temp gauge, but those are larger in diameter. I have not figured out a safe easily viewed place to mount it yet. I am not having faith in my fan right now, it kicks on when it wants to and I know it smells hot, and it won't kick on or flash "hot". The fan doesn't sound weak, and when it does kick on, it sounds normal. I am not going to get burned by polaris and their poor engineering again.

  11. Hi, I was able to pull on the manual and turn the engine over , to me thats tell me its not seized at least..

    The bike is now a the dealer. They just called to say they are not getting compression and are going to look at it.

    I suspect valves..

  12. Mine would still crank and pull over once I let it cool down. It was galled but not bad, but still wouldn't start. Maybe you will get lucky and have only a ring frozen in your piston with no galling. It was faster for me to just buy a new piston, cylinder, rings, banjo crush gaskets and cylinder base/head/exhaust/timing cover/valve cover/thermostat gaskets. Rather than wait for things to be mailed out, bored over and mailed back. It took me less than 2 hrs to put everything back together and have it running once I started on it. Very simple motor to work on.