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Hello, new to the forum. I have an overheating issue that i dont think is "typical". Ive owned this scrabler 850 about 2 months, knew thew previous owner personally, never overheated. I rode for about 10 hours a couple weekends ago, came home from the ATV park, washed it, and took it for a ride the next day. about an hour into this ride is when it first overheated. let it cool, tried again, no go. noticed the fan seemed to stop blowing heat unless it was idling. called someone with a trailer. Since then i have replaced the thermostat, checked the water pump twice (no drips from weep hose either, and i made sure that was clear), checked all hoses, flushed the radiator, done a pressure test (passed polaris spec with 3x the duration they want) bled it after each reassembly (about 4 probably). rad is always full. pump seems to work (sucks down when i hit the gas) old thermostat tested ok and it has a new one anyhow. tried coolant temp sensor from another 850. another cap. fan runs and at about the right temp, but never cools back off only climbs. first time working on it at night last night, i noticed the header glowing very red, riding around the lawn in low at about 2000-2500 rpm for maybe 5 minutes, so im not thinking this is coolant related at all but i could be wrong still. 3 local dealers say i have done what they would do. hope someone on here has some insight, i didnt have good experience with my last polaris, and this one doesnt seem any different...
 

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Just a thought
try running a colder range spark plug.
Are you running ethanol?
Try running without the thermostat see if that helps. This isnt a long term solution just a test
Try dropping your old thermostat into boiling water. Does it open up? Is it oriented the right way in the engine? I have seen these put in upside in a few cars before, so anything is possible.
When you drained your coolant, was it clean or did it have crud?
 

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Discussion Starter #4
1) i would agree with the plugs, but that shouldnt come out of the blue needing cooler plugs. its run on these plugs for 1-2 years give or take, previous owner lived here and rode where i do.
2) no ethanol
3) the thermostat can only fit in one orientation, can only be spun 180. nor would it flip over when im going down the road in the first place to cause the initial overheat.
4) yes the old one opened and i had a temp probe on my dmm in the water too, correct temp.
5) coolant always full and clean.
per the service manual, i need a fuel pump (6-8psi down from spec), and that can cause an overheat in the troubleshooting section, so im starting there. i work on cars every day and ive been through the cooling system forward and backward twice over, im fully confident in that it is not a cooling system issue.
 

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1) i would agree with the plugs
I disagree with the colder plug - the heat range of the spark plug refers to the temperature of the tip of the plug when the engine is at normal operating temperature

4) yes the old one opened and i had a temp probe on my dmm in the water too, correct temp.
If you had a probe in the coolant and it was correct, then how is it you determined it is overheating? Sounds to as as though it is fine. Is it just that the fan does not come on or what?
 

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Discussion Starter #6
1) i would agree with the plugs
I disagree with the colder plug - the heat range of the spark plug refers to the temperature of the tip of the plug when the engine is at normal operating temperature

4) yes the old one opened and i had a temp probe on my dmm in the water too, correct temp.
If you had a probe in the coolant and it was correct, then how is it you determined it is overheating? Sounds to as as though it is fine. Is it just that the fan does not come on or what?
i had a probe in the water when i had it in the stove to test the thermostat, thats how he was saying to test my old one, i already did. the overheat light comes on and it goes into limp mode. the fan runs fine.
 

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Discussion Starter #10
What year model is this "scrabler 850"?
2015, no need to be a dink because i forgot an m, big deal.
I don’t think he was being a dink. Just playing with ya. That guys probably forgotten more than we’ll ever know about these machines. He’s actually very helpful to many.
i never said anything otherwise, just seems like he doesnt believe me that theres even an issue, and grammar isnt what i came for advice on... pretty sure being able to hear the coolant boiling when i shut it down, accompanied by an overheating light is probably an issue. i figured that the temp light is coming on should be obvious.
 

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Discussion Starter #11 (Edited)
my thoughts after the glowing bright red/orange header is a lean condition... but my plugs dont look very white. im down on fuel pressure. it does seem to backfire once in a while especially warming up.
 

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At what temp does the fan come on and how long after the fan comes on does it start to boil? Have you tried running it with the thermostat out? When you flushed the radiator, was that internally or externally? It's usually debris or dirt obstructing air flow through the radiator that is the cause of most overheating situations. If it's idling and boiling the coolant, will spraying the radiator with water stop the boiling? Is there a kink in a hose? Have you removed the hoses and inspected them on the inside for a liner collapse? When you accelerate the engine and the coolant 'sucks down' where's it going? On the cooling systems I have worked on the coolant never 'sucks down' - it either simply circulates or blows out of the radiator neck due to a compression leak into the water jacket. Are you using water or coolant? Water boils at about 212 degrees F while 50:50 coolant boils at about 223 degrees F, but water is a superior coolant to antifreeze as it makes better contact with the metal of the engine an heat transfers faster from the metal to the liquid - down side to water is it promotes corrosion while antifreeze inhibits corrosion - use distilled water for testing, but operate with coolant.

I think ultimately you will find there is air trapped within the cooling system or the radiator is obstructed.
 

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Discussion Starter #13
the fan seems to come around right about 200 with my probe on the tstat housing, id say no more than 10 mins idling the temp light comes on, riding around the lawn maybe 2-3 mins after fan kicks on, the light will come on. i have not tried with no tstat. i have washed the outside of the rad and flushed the inside with a garden hose for like 10-15 min. i cant see getting it any cleaner without some sort of etching wheel cleaner or something. i cant find any kinks or anything in any lines. it doesnt suck down alot when i hit the gas, but noticeable. how would i go about testing the hoses to see if theyre de laminated?
 

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Discussion Starter #14
At what temp does the fan come on and how long after the fan comes on does it start to boil? Have you tried running it with the thermostat out? When you flushed the radiator, was that internally or externally? It's usually debris or dirt obstructing air flow through the radiator that is the cause of most overheating situations. If it's idling and boiling the coolant, will spraying the radiator with water stop the boiling? Is there a kink in a hose? Have you removed the hoses and inspected them on the inside for a liner collapse? When you accelerate the engine and the coolant 'sucks down' where's it going? On the cooling systems I have worked on the coolant never 'sucks down' - it either simply circulates or blows out of the radiator neck due to a compression leak into the water jacket. Are you using water or coolant? Water boils at about 212 degrees F while 50:50 coolant boils at about 223 degrees F, but water is a superior coolant to antifreeze as it makes better contact with the metal of the engine an heat transfers faster from the metal to the liquid - down side to water is it promotes corrosion while antifreeze inhibits corrosion - use distilled water for testing, but operate with coolant.

I think ultimately you will find there is air trapped within the cooling system or the radiator is obstructed.
forgot to quote you so you get the notification.
 

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Discussion Starter #15
At what temp does the fan come on and how long after the fan comes on does it start to boil? Have you tried running it with the thermostat out? When you flushed the radiator, was that internally or externally? It's usually debris or dirt obstructing air flow through the radiator that is the cause of most overheating situations. If it's idling and boiling the coolant, will spraying the radiator with water stop the boiling? Is there a kink in a hose? Have you removed the hoses and inspected them on the inside for a liner collapse? When you accelerate the engine and the coolant 'sucks down' where's it going? On the cooling systems I have worked on the coolant never 'sucks down' - it either simply circulates or blows out of the radiator neck due to a compression leak into the water jacket. Are you using water or coolant? Water boils at about 212 degrees F while 50:50 coolant boils at about 223 degrees F, but water is a superior coolant to antifreeze as it makes better contact with the metal of the engine an heat transfers faster from the metal to the liquid - down side to water is it promotes corrosion while antifreeze inhibits corrosion - use distilled water for testing, but operate with coolant.

I think ultimately you will find there is air trapped within the cooling system or the radiator is obstructed.
still overheats without a thermostat. if we could figure out why my radiator seems to go cold when im actually riding/on the gas, wed have the issue. when the light just now came on, the radiator was cold and only the upper rad hose was hot. lower was completely cool to the touch.
 

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Discussion Starter #16
At what temp does the fan come on and how long after the fan comes on does it start to boil? Have you tried running it with the thermostat out? When you flushed the radiator, was that internally or externally? It's usually debris or dirt obstructing air flow through the radiator that is the cause of most overheating situations. If it's idling and boiling the coolant, will spraying the radiator with water stop the boiling? Is there a kink in a hose? Have you removed the hoses and inspected them on the inside for a liner collapse? When you accelerate the engine and the coolant 'sucks down' where's it going? On the cooling systems I have worked on the coolant never 'sucks down' - it either simply circulates or blows out of the radiator neck due to a compression leak into the water jacket. Are you using water or coolant? Water boils at about 212 degrees F while 50:50 coolant boils at about 223 degrees F, but water is a superior coolant to antifreeze as it makes better contact with the metal of the engine an heat transfers faster from the metal to the liquid - down side to water is it promotes corrosion while antifreeze inhibits corrosion - use distilled water for testing, but operate with coolant.

I think ultimately you will find there is air trapped within the cooling system or the radiator is obstructed.
latebird, ive tried it now without the thermostat, and swapped out the radiator (not new, but known good), just to take those out of the equation. when i pull the upper radiator hose and crank it over it moves a fair bit of water... but still when my overheat light comes on my radiator is completely cold as well as the lower radiator hose, the upper radiator hose however stays really hot no matter what... this seems to me like an internally plugged radiator, but it just cant be as ive had 2 different ones on it (between the two machines in my avatar).. idling the radiator and both hoses all get warm pretty evenly. ive been testing with straight water before you posted to.. ive double checked the hoses for any kinks.. it doesnt blow out of the rad at all with the cap off, only circulates as you say, but doesnt seem to have a ton of pressure behind it in my opinion... still when i hit the gas the level drops, maybe like until the very top coolant passage in the radiator is above/at the water line instead of full to the cap when its not running... my pipe is still glowing under minimal load 2-3k rpm around the yard once or twice and its cherry red. whether thats part of the overheating issue or not im going to be addressing that too.
 

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Just for giggles since you said you have a thermal probe check your oil temperature after it has warmed up. Turn engine off and check oil temperature and look for any signs of the oil over heating. The temperature should run somewhere between 212-270 degrees F. Don't let the probe touch the case just oil.
 
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