I am having a overheating problem on my sp500 1997. I have read lots of posts and just about the same advice from everyone. Here is what I have done: I have replaced the fan motor it was bad. I have tested the new one just to be sure before I put everything back together it worked fine. I have tested the thermostat in boiling water, it was not stuck it worked fine too. There is no oil in the coolant either. I will check tomarrow if the radiator fins are clogged will clean if they are. If they do happen to be clogged shouldn't the fan kick on anyway?
What else could I check or replace? While I am replacing things, should I replace the tstat, radiator cap and thermo sensor? One more question how do I purge air that might be trapped in the system? I have read that this could cause overheating.
Thanks in advance for all the advice.

 

Take out the thermo sensor (that kicks the fan on), hook it up to an ohmmeter, & drop it in a pan of water on the stove. As it heats up, the resistance should decrease. For accuracy, I'd have a thermometer on hand to see how hot the water is. Should be little or no resistance when the temp is at or near the temp at which the fan should be on.

Purging air is fairly easy, just takes patience. I keep the cap off, fill it up & squeeze a hose repeatedly to force the bubbles out. Then I fire it up following the same procedure. Then, throw the cap on, & slightly overfill the overflow tank, so when everything cools down, it will draw in the excess coolant & naturally purge any air that's left over.

 

Make sure the radiator is clean the front may look fine but the back is where the mud gets packed into it needs to be clean. Test the fan sensor and make sure it is working. If the thermostat worked fine then there is no reason to replace it. For the radiator cap make sure there is nothing obvious is wrong with it if you do need a new one you can go to napa and get the same cap for $6 while polaris chages $30! I have the part # if you need it. To purge the air out raise the front end of it up in the air a ways and let it idle and keep adding coolant if it drops down. Does it overheat like it is getting really hot or is it just all of a sudden spitting coolant out of the resivor bottle after just a little while of running? I had this happen on my scrambler and it was a head gasket and there was no sign of it burning coolant or coolant getting into the oil it would just spit coolant out of the resivor after runing it for a while. But check the simple stuff first.
Jason

 

the first thing you should be looking at is the rad. for being plugged front and back. in the fan works then try the temp sensor. yes air will make it over heat. what i do is simple, just leave the cap on the first notch and let the fan cycle thru a few times. the only way air to be in the system would be if it got drained or lost alot of anifreeze.

 

Thats what i thought was wrong with my scrambler is that there was air in it so i kept bleeding if and i did that about 15 times and everytime after that it would do the same thing. My head gasket was letting a little air into the water jacket everytime the engine would build extreme pressure until it put over 13lbs into my cooling system then the cap would spit it back into the resivor bottle and drop my coolant level down in my radiator but my scrambler was not overheating at all. I put a new head gasket in and it has been fine for awile now.
Jason

 

what do you think took out your head gasket, any idears. did you overheat it alot at one point in time?

 

If your fan is not coming on, I'd check out your fan switch/ thermo sensor/ etc. some of the guys mentioned. Mine went bad at 120HRS 400 miles. The radiator loads up with crap also, like everone says too! Hope you get it straightened out!

 

Nope never overheated it, i tore the engine apart for crank shaft endplay (in and out) because there was a thrust washer missing and it was out of spec. But i put a moose gasket set in and it failed! NEVER use anything other than OEM gaskets i haven't had a problem since.
Jason

 

oh i see. yea im a firm beleaver in oem parts for engines as well, but thats just me.