Another overheating thread. I have looked through several of the others and wanted to kind of narrow it down some.

I have a 2000 Sportsman 500 (non-HO). I can put around all day at about 15-25 mph and it does fine. In the last year, I have replaced the thermostat and water pump gasket. About 3-4 years ago, I replaced the head gasket. I can hear the fan running normally at slow speeds. It comes on and off intermittently as it should when the temp goes up. I can open the radiator cap and at idle, there is barely a trickle of water circulating through the system. As I rev the engine, I can see larger volumes of water going through, enough so that it spews about 1-3 feet in the air above the radiator cap. I have checked the radiator, both front and back and I see no debris or mud in it. I had the entire radiator out a few days ago and confirmed this. I burped the system afterwards by elevating the front to about 45 degrees and running it at idle for about 30 minutes.

The problem occurs when I go above 35 mph. After only a few minutes, the overheat light comes on and it starts spitting and spewing water and steam from the radiator cap. The outside temp is around 55' when this was occurring.

I am thinking this could be a bad radiator cap, but I am not sure. I will post a picture of the cap if needed. Is there anything else I should be looking at?

Thanks.

 

Try a new cap, sounds like its not hoding the pressure. if you take the old one with you the aoto parts store can probably find one

 

I don't think it's going to be the cap. If the light comes on, that engine is getting hot. The only thing the cap pressure does is keep the coolant from boiling.

Could be quite a few things. Does it seem like your using coolant?

 

I own the same quad. Our model is known for the radiator fan switch to go bad. If you search these forums, including my posts, I think you'll see a common issue across 2000 SP500 owners.

If the fan is cycling on and off as it should, then it shouldn't be the radiator fan switch... but, I'm just saying this is a known issue with our model. I replaced it, along with a new radiator fan direct from SPAL for $75, and haven't had an issue since. I also added a temp gauge just to keep on eye on things (got sick of overheats) and a fan override switch... both are worth the time/$$$. Fan should be kicking on around 210*, and off around 170*.

How you describe the water pump flow is normal IMO. Slow flow at idle... faster with engine RPM. I'd look elsewhere for your problems.

Personally, I also power wash out the radiator after every ride. Learned this one the hard way.

 

We had similar problems with my son's ATP 500HO. I would check the cap. It's what was the problem with ours and is a cheap fix.

 

try to jump out your fan so it runs all the time so you can rule that out.then remove your radiator and inspect it really well for pinched water vains and try and get some cleaner and let it set in the radiator then run the hose thru it for awhile.sounds like a clogged radiator

 

sounds like the cap to me, from what ive seen, if they overheat, they will get rid of the pressure and boil the coolant down in the coolant bottle, not out of the cap

 

I had a simliar issue with my 600 and the filler neck of the radiator got warped due to the machine overheating. I replaced the filler neck and the radiator cap and no more leaking.....

 

As someone else said replace the cap. And don't be foolish and pay $35 for one at a dealer. You can get the cap at any auto parts store for about $8