2001 Polaris Sportsman 400

Very short routes, the unit is overheating. I cleaned the radiator fins, some dust and stuff came off, looks shinier now. Now I want to try and purge the system of air. Here's my questions:

Park flat, engine cool, jack up so the front end is just off the ground. Pop off the radiator cap. Should I see fluid, or should I not?
Start the unit with cap off and let it cycle a couple times. I assume this means let the fan cycle. Should I be throttling her during this run time or let it get hot just by idling?
Then top off the radiator. Level up to the overflow tube?

Yesterday the radiator light came on, and I drove another thousand feet, and when I parked, the fluid in the overflow was just bubbling like crazy. As soon as I shut the engine off, literally within seconds, the fluid calmed right down. Was it boiling or just bubbling air?

After this, if it's still whacky, I guess I will look at the impeller and sensor.

 

Just up enough to get the wheels off the ground. Idle only,not throttle. You should see a little fluid circulating.You can squeeze the hoses to assist in purging any air. It may take several minute to get all trapped air pockets out so be patient and let the fan cycle on and off several times during this process. Simple things like a leaking radiator cap can cause problems also. 13 psi cap is cheap to replace if you have doubts on it. The hot light should not come on during the purging process. If it does,the radiator sensor that kicks the fan on could be getting weak and not letting it kick on quick enough. After purging air the radiator level should drop,top it off and replace the cap and top off the over flow bottle. Then test drive. If it still over heats,then could be the radiator is still dirty especially at the back around the fan is where mud accumulates,or could be impeller problems. I've seen them loosen up on the shaft and also melted fins from cavitation when air is in the system. There's a lot of crooks and bends in this system and does take awhile. Plus another weak point is the plastic filler neck that can warp/distort. Make sure the radiator cap fits snug on it.

 

Ok, about how long should it run before the fan kicks in, do you think?

Thanks.

 

Fan kicks on at approximately 190 degrees,kicks off approximately 180-185 degrees.Sensor isn't designed for the fan to stay on long unless machine is at an idle or slow moving,under loads,etc then the fan will continue to run as coolant temperatures will remain high under these conditions.

 

Ok. I ran her for about 15 minutes, and the fan did not come on, the hot light did not come on, and I saw no fluid movement. My coolant recovery jug sat below "min level" but nothing added or removed. Guess I need to let it idle more...
The radiator felt ice cold during this time (the fins). The exhaust shield and that stuff was freakin piping hot...

 

Check the hoses for pressure and heat. If they're cold same as the radiator fins,then I'd be checking the impeller.If they feel full and warm,top off the radiator and recovery bottle and take it for a spin.If hot light comes back on then I'd check into the water pump impeller.

 

OK FINALLY I get some thing to happen .
Idling for twenty minutes. Hoses off the radiator stone cold, can compress them pretty easy. The impeller housing was quite hot, hoses off of it not warm at all. As I got ready to shut it off, antifreeze started bubbling out of the open radiator.

Think its the impeller ?

 

Sounds like an impeller problem if the hoses are cool and you can compress them.

 

I have attached a picture of what I think is the impeller housing. There were 4 8mm nuts that I removed, but the housing showed no signs at all of budging. There was a 10mm bolt I removed, but only antifreeze came bubbling out of that. Do I need to remove the case that has the pull rope?

Thanks.

 

Easier if you just remove the hoses. Just loosen the clamps,pry around the hoses with a screw driver.Have a drain pan to catch the coolant.Remove the 4 bolts and just tap the cover off. The 10mm bolt is just a drain/bleed screw for the w/p cavity. Takes too long if you drain it that way.