I suppose the water pump needs replacing, as it doesn't seem to be moving any more coolant. Where can I get a replacement pump, cheaply? Is it a job I should try or do I really need a shop to handle it?

 

Try jacking the front end up with the tires off the ground and leaving the radiator cap off. If the fan is operating properly after several cycles any trapped air should be purged. You can top off the radiator and overflow bottle and replace the radiator cap.If this doesn't help check under the water pump cover for any signs of seal leakage through the weep hole. You can remove the cover and check if the impeller is tight and the impeller nut hasn't backed off allowing the w/p shaft to turn and not the impeller. Plus doesn't happen often,but if it's gotten hot several times,especially from trapped air in the system, the pump cavity can run super hot enough to melt the fins on the impeller not allowing it to push coolant through the engine.If it's not leaking the w/p seal should be okay.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse Helps to know what year model you have! Could be other things to check out..Plus dirty/mud caked radiators,especially around the fan area were a common cause of overheating problems also.

 

I really want to find time for this job, but I do want to thank old Polaris tech for his reply; very, very good information to have.

 

I did those first couple steps, to ensure that any air would be expelled by the radiator. I drove the machine a little bit yesterday, with no overheat. I did stop and check the radiator, after it had cooled a bit. The coolant in the radiator was very warm, so doesn't that mean it had been pumped from the engine?

I just can't get it to the shop at the moment and I must avoid causing serious issues to the machine. Opening up the water pump behind that cover looks pretty serious, but do I need to do that to just try a new thermostat?

 

Don't worry about the w/p cover or the thermostat housing! Just make sure the coolant is cycling through the radiator,yes it will be hot. Just run with the cap off and let the fan cycle on and off several times. If it runs ok without the hot light coming on,then top off the coolant,replace the cap and top off the recovery bottle. Thermostats are one of the last things to have problems on the 500s. Trapped air is the main culprit,2nd is mud clogged radiators causing over heating.

 

Once you burp the air out , just look down the rad filler hole while the ATV is idling. You should see the coolant moving. If so then you know its not the water pump.
Not to common for the water pump to fail,heard of the water pump seal more but that cause a water leak not stops water circulation.

You know the water is flowing and you have no air lock if both the top and bottom rad hose are firm and very warm after warm up.
If the bottom rad hose is cooler and soft the water is not flowing yet.

 

I want to thank you fella's for the help, very much appreciated at this point.

I just ran the machine for a few minutes with the radiator cap off and here's what I found.

1. "Hot - check engine" light comes on after about 15 seconds of running, always.
2. When it said "hot" initially, I put my finger in the radiator and the coolant was in fact cold.
3. About 10 minutes into it, I could feel heat beginning to come off the engine, but the fan never came on. The radiator was getting very warm.
4. I did a couple restarts and idle sessions, but I could not get that fan to come on. It's funny, because I'm pretty sure I've heard that fan recently, but it didn't come on at all today.
5. In the end, I believed the "Hot" warning, which was still on, as I couldn't touch the coolant in that damn hot radiator. That must mean the water pump was actually moving fluid to and from engine.

I couldn't sense any coolant moving in the radiator really, though it did begin to overflow just a bit. I didn't see much change in the backup reservoir.

I'm not sure where to go from here...

 

Would help a little better to know the year model. Check that the fan blade isn't obstructed,run 12 volts direct to the fan motor and see if it works. If it does,then possible radiator sensor short or an ecm module problem if it's a 2005 model or later.

 

I did move the fan freely by hand, so there are no obstructions. I'm not sure how to run 12 volts directly to it; I can make it come on in some way?

Beyond that, I believe I'll need to trailer it to service, when I can this summer.

Am I risking causing more damage until then if I run it for a few minutes, and then let it cool off?

 

Just disconnect the fans two wires and run jumper wires from a battery to see if it works. If it does the problem is usually in the radiator thermal sensor or the plastic sealed 10 amp fan circuit breaker under the front panel may be corroded. Just use a test light or meter to see if the red wires on each side of the breaker pouch have power. If it does,I'd replace the radiator sensor.Item #3 is the fan sensor.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse
Item #21 is the fan sensor.http://www.cyclepartswarehouse.com/f...2002&fveh=5582