You might have to get back on that Fan sensor in the rad. If the coolant gets to a certain temp that is what tells the fan to run to turn on.

Working senor + working fan+ hot coolant = running fan.

Something in that equation is the trouble if its not a Air lock in the system.

 

Another thing that may be missed that I don't think I saw is to take the radiator off. When I had overheating problems on a 2006 Sportsman X2 with the 500 I tried everything and then had the radiator taken off and there was a ton of mud caked in on the corners. Enough, that when it got completely cleaned out, it didn't overheat anymore.

 

I know this thread is old but I still have yet to fix it. I have a working fan but it kicks on Id say right after there is coolant boiling in the resivor. If the fourwheeler is lifted with the cap on or off the fan works fine and the fourwheeler doesnt throw the over heat light but there will be coolant boiling or steaming out of the reserve tank. The fan also worked when it was on the ground with the cap on and didnt over heat but still the coolant boiling and steam coming out the reserve. then when i turn it off its sucking back in what coolant is left or air. Which leads me to have air in the line if I run it again after that. I dont fill past the min when its cold or the max line when its hot. any suggestions?

 

Did you ever check the impeller also?? I've found some either loose not spinning on the shaft or have melted from from trapped air. This can keep the coolant from flowing enough from the system purging trapped air. Also the fan has a sealed 10 amp circuit breaker under the front panel. Slice the pouch and see if the breaker contacts are corroded. This can cause a fan to short cycle or not kick on properly. You can get them at any auto store. Plus have you cleaned the radiator as mentioned. Caked on dirt/mud especially around the fan area causes a lot of overheating problems. This model does take a while on some to remove all trapped air also because of the way the hoses are routed.Squeezing the hoses while the atv is elevated helps. Plus if all these things checks out the radiator sensor itself could be weak,delaying the fan from working properly,but still sounds like you have trapped air or it's not able to purge the air from the system .

 

I have checked the prop and it doesn't have play but I can spin it with my fingers but its not easy to spin. The circuit I already checked and it works fine and no corrosion. In going to try again tonight to get the air out because it sucked some back in after I turned it off. Also I fully cleaned the rad by taking it off. And replaced the sensor on the bottom of the radiator.

 

Ran again tonight. After I thought all the air was out of the lines. (all my lines were firm and warm). The fan kicks on after I have boiling coolant/steam coming out of my reserve. the over heat light never came on while it was running but it kept boiling coolant till it was just steam coming out. also i should say I have another rad cap but found out it was 16 psi not 13 so i went back to the old cap.

One question I have is that when the over heat light sensor is on should the fan automatically come on? bc that doesnt happen. Also if I unplug the sensor would that make the fan run bc I read that somewhere online and it doesnt happen either.

Last thing is I really want to thank everyone for all their time and help, Im sorry this hasnt been solved yet. Ive never had a problem last this long. So thanks again to everyone.

 

I don't know much, but I do know that the fan is supposed to start running before the overheat light comes on.

 

Did you ever slice this pouch open to check the fan circuit breaker? Item #2 at the top of the page. Located under the front panel. It could be the cause of the slow acting fan. If it's corroded just replace this 10 amp breaker at any auto store. It sounds like it's either this or a radiator sensor about to short out "IF" you have all the air purged.

 

I checked that circuit breaker and there wasnt any corrosion so now I just need to find a replacement just in case. I did check it and it worked though. just hooked it up to a light bulb and battery and it worked. Another question is when getting the air out of the system with the cap off after the thermostat opens the coolant is pretty violent. It will just over flow most of the time even before its really hot. is that normal?? im assuming its just the air in the lines but then it keeps happening which ends up pushing a lot of coolant out.

 

Have you checked each red wire end on the circuit breaker to see if it has power going through it after it runs awhile? This is a thermal type breaker and will shut down if it gets hot and not kick the fan on,or work intermittently. You can also pull the thermostat,remove the rubber seal and place it back in the housing and try it without a thermostat and see if it still spews out the radiator. You said you could turn the impeller?? The impeller should be tight and only be able to spin when the engine turns over. Plus have you removed the radiator to clean it? I've had to do this on some very mud/dirt caked ones that were over heating. I'm just fishing around again.....