Well this is an update to my buddys 05 700efi sportsman overheating after weeks of troubleshooting this thing which by the way thanks to everyone for there suggestions.
We flushed the entire system, checked the water pump, all the relays, all the fuses, the thermostat, cleaned the radiator, checked the fan, Installed a new filler neck, a new radiator cap, new radiator fluid, purged the system had 2 thermostar switches checked by a dealer which we were told 1 was better than the other and still no luck. So we decided to install a brand new thermostar switch and "BAM" everything seemed to be doing what it was suppose to be doing as in normal operation the overflow bottle would fill from the low mark to the high mark as it would warm up to temp then the fan would kick on as it should once it hit the high mark and draw the fluid back down to shut the fan off to us it seemed we finally had it after all that work. He rode the machine around his yard a little and we would watch it, it was still operating fine this is in a hrs time give or take then all of a sudden he went to park it and let it cool completely to top off the fluid and "BAMMO" the fluid just started to spit out of the overflow bottle again as if it was overheating again what the hell gives!!!!!!! any other input on this nightmare would be so great.....
Thanks

 

did you purge the system after you replaced the thermostat? on some models it's hard to get all the air out.

 

let it run for awhile w/ the rad. cap loose to as mentioned above to purge out the air to rule out an air bubble. other then that i can't imagin what the heck would be doing the over heating.

 

You didn't mention checking for a restricted or plugged exhaust.

Also, I had an engine, not an ATV, that would only overhead when the engine was put under load. It would sit there and idle all day long without over heating, but if you made it work hard, it would boil over after a while. It ended up being a small crack in a head.

On the other tread someone mentioned standing it on end to get the air out. Also mentioned, was a slipping water pump, which could slip on the shaft when heated.

Can you leave the thermostat out and see what happens. I don't believe much in the stove boiling test. Try a new one instead. Good luck, this must be frustrating.

 

We did'nt replace the thermostat we checked it in a pot of boiling water to see if it opened and closed which it did so we assume it should be good however I just wonder if it is not opening and closing as fast as it should be like a new one would??


We did replace the thermostar switch.

 

No we did not check for a restricted exhaust which I dont think is causing it
I am not sure if you can leave the thermostat out or not to test it Stendori might know that answer?

 

Have you checked your voltage while it is running to make sure there is enough power to operate the fan. Just curious since I had a similar problem that was caused by a bad stator and not putting out enough power to run the fan all the time.

 

How hot in overheat? Actual temp you are talking about? How did you check the water pump(did you install a pressure gauge to check w/p pressure) only by looking at it? Maybe those bubbles are coming from the combustion chamber check with a dye check or check for building pressure in the radiator with a gage. All the parts you have been throwing at your machine are adding up maybe time for a real mechanic check out your dealer huh!

 

You say you "cleaned" the radiator - did you actually remove it from the quad & soak it? I had a similar issue on my '05 SP700. I cleaned, cleaned & cleaned the rad as best possible. Finally I removed it from the quad - I was absolutely stunned at just how much dried mud was still in there.

 

We did not remove it, we just air hosed it front and back, this machine has never even been in any sort of serious mud just through hay feilds and such it is used for hunting and trail riding no mudding...