Hey all - first post as I am new here. I have been using your other forums so I might as well sign up!

I have a 91 polaris Trail Boss 350L 2x4 that was just purchased. I am now getting a HOT sensor as it is overheating. I filled the antifreeze (may have overfilled it) and took it for a ride. Within 5 minutes the HOT sensor comes on. I burped the antifreeze using the 10mm bolt on the engine but it only spurted out. When the key is turned the fan comes on immediately. Even when it was not running prior.

Any help would be greatly appreciated and thanks for having me!

 

Bleed air from the 10mm bolt with the engine off only.If the fan fails to come on and the hot light comes on ,the radiator sensor may be the problem as they were prone to burnout if coolant got below the top of the radiator.This item is NLA from online sources. You can take it and match up the sensor at most auto stores.Item #30 in the parts break down.

 

Thanks! I will give it a shot tonight. With that said, when I turn the key the fan automatically comes on so it may be bypassed - right?

 

If the fan comes on when you turn the key on, the switch in the radiator sensor has melted and powers up the fan. Sensor need to be replaced. You may have to splice your wiring into a new sensors as most will be just a two pronged type replacement,no wiring harness.The pic is just an example of a sensor. If the hot light comes on,you may still have trapped air in the system.

 

Okay, so bleed it with the engine on or off? Also, part 30 on the diagram is for the overheating issue (possibly)? And the photo you attached has to do with the fan coming on when the key is turned on? Thanks again for your help.

 

Bleed with engine off.. Make sure all air bubbles are cleared before you close the 10 mm bolt. Item 30 and the sensor pic is one and the same only yours has the harness built in. It's what triggers the fan when the temperature is around a 175 degrees. Here's a pic of your old sensor. Just make new spade connectors for the replacement switch.

 

Thank you! I will give it a shot and update later on tonight!

 

Burped it last night with the engine off - some antifreeze was flowing out and then stopped. The fan still turns on when the ignition is in the ON position. I looked at the sensor that you had said to check - looks like the wires were cut/broken and never reconnected. The previous owner must have over ridden the sensor and went straight to the ignition. Will this cause the ATV to overheat if the fan is wired to come on when the ignition is turned on?

Thanks again!

 

Also, when running and the HOT signal comes on my tube from the rad to the engine is hot but the other tube that runs back to the other side of the rad is cold. If that helps any.

 

No this wouldn't cause the engine to over heat,but it needs to be fixed so the fan can cycle on and off properly which extends the life of the fan. If one hose side is hot and one cold on the radiator then still sounds like trapped air or a dirty radiator. You can generally open the radiator cap and see if coolant is at least flowing back,plus a good idea on this machine to bleed the head bolt first,jack the front end up and leave the radiator cap off. Air pockets can also be between the radiator and the water pump.This would help take care of that.