Again jack the front wheels off the ground,leave the cap off.Let the fan circulate on and off about 3 or 4 times. Check for any noticeable leaks especially around the radiator itself and hoses and also the water pump cavity weep hole that could indicate a blown water pump seal. Top off the radiator as the level goes down. Replace the cap and top off the recovery bottle. If after driving awhile the bottle is empty or very low,pressure check the radiator. Should hold 10 psi with no leak down. If it wont hold the 10psi pressure and no external leaking noticed,then coolant could be seeping past the head gasket into the combustion chamber. If a head gasket leak is large enough there may be a sweet smell from the exhaust and sometimes smoke.

 

Thanks OPT.

After riding an hour, should the radiator cap be hot? Should the fins of the radiator be hot?

If I jack the front end up and run it with the cap off, what usually happens is the coolant level in the radiator slowly rises and then comes over the top an spills out (like someone slowly sitting into a very full bathtub). So do I let it do that and just keep filling it? It seems to take a long time for the fan to come off when I do this, yet when we ride, the fan comes on in a reasonable amount of time.

I will do that and look for leaks. The Overheat light did not come on, so maybe I just didn't fill the system up enough.

 

That's possible also,plus yes the radiator should be warm along with the cap. If coolant is just flowing out,one other thing is the water pump impeller itself may be just spinning on the shaft or melted down from heat and cavitation from air pockets not allowing coolant to circulate.

 

Ok, so I am really frustrated and thinking of just selling her for parts....

Ran it for about thirty minutes and realized I was rapidly losing power, bogging down when I press the throttle. I reach in front of the radiator and feel no air, but the fins are SCALDING hot. The fan is not running.

So I am going to let her sit and cool, but what the heck is going on now? I will test the fan in the unlikely event it just died. What would the sensor look like on the radiator to tell it is hot and needs the fan to come on?

 

Pull the connector at the fan.You can jump this connector to the battery to see if the fan is working ok.If it's not,Spal fans are cheaper online than any dealer.Spal Electric Fans - The Fan Man https://webstore.spalusa.com/en-us/p...rcycleatv.aspx Hopefully the fan motor is ok and it's just the sensor that's shorted on the lower right of the radiator. Item#20 on the parts break down. 2001 Polaris SPORTSMAN 400 (A01CH42AA) Cooling System | Cycle Parts Warehouse No sense paying 62 bucks for this sensor when you can use a Wells Sw526 from any auto supply for half that. The sensor closes contacts when a certain temp is reached and provides the ground path for the fan to kick on. All you have to do is cut the connector end off and use your old connector. There is also a fan circuit breaker in a sealed pouch under the front panel. Make sure you have voltage on both sides of the red wires. If in doubt slice the pouch open to check for corroded wires. These breakers are cheap at any auto supply.

 

Any way to test the sensor or just, assume it is bad? The Fan Works Fine When Fed 12v.

 

Check the resistance on the sensor leads when cold. Drop sensor in hot water and resistance levels should drop if the sensor is good. If there is no change then the sensor has shorted out which was a common problems on these. Sensor just has an internal switch that bridges and completed the circuit(ground path) for the fan to kick on. Don't forget to check the fan circuit breaker in the sealed pouch. Should have 12 volts on each side of the red wire leading in and out

 

Thanks OPT. .breaker tested good. Sensor displayed no change when dropped into almost boiling water. Have a new sensor on order.
Sheesh, the price of that radiator....I expect them to make a profit but 499 for that tiny radiator!!

 

You order an oem sensor or the SW526 for about 25 bucks or so? If radiator is junk you can get them cheaper than any dealer also.199 bucks. http://www.ebay.com/itm/like/262492080030?lpid=82&chn=ps&ul_noapp=true

 

I ordered the OEM sensor for about $25. I have seen "used" radiators pulled from dead ATVs on Ebay, cleaned up and guaranteed to work, for less than $50.

I should have wondered...more than a few times when I have done the "idle with the cap off and front wheels slightly off the ground" the fan would never come on. Yet most times when riding, it would come on.

Hoping the sensor fixes the issue...