Hey guys, im new to the site. Need help. My 400 is overheating really quick. We are not riding it just starting it up and idling just a 2-3 minutes. the hot engine light is flashing as soon as you turn the switch on even when cold? don't know whats up with that. when it gets hot it spits water out of overflow tank, fan does not turn on at all. we checked it wiring straight to battery and fan does work. we took thermostat out and tried it, and it still runs hot very quickly. Is this the water pump bad or something else. the outside of radiator is clean and the screen is clean. If it is the pump how hard are they to change? It looks like just 4 bolts but I could be wrong. Hopefully someone can help my kids are wanting to ride bad. The thing has been down for a long time I just have not had time to get to it.

 

If the hot light turns on even when the atv is cold,then probably the ecm module has failed.It controls the fan along with charging,etc. Item #10 on the breakdown.Dirt Cheap Yamaha & Polaris OEM Parts & Accessories – Cycle Parts Warehouse If you still have the BLACK finned Chinese module(some are still out there) then it's a no cost to you repair as it was in the model range recall list of faulty ecm modules. If it has the updated silver US made Sure Power module they can still fail.I've had to replace multiple modules on the same atvs. Several on the forum have also. If this is the case,then the replacement cost is out of your pocket.Huge ATV Recall by Polaris - Sportsman and Scrambler

 

I hate to sound stupid, but where is this module and how do I know which one it has?

 

Click on the first link I posted. It's the parts break down.. Item #10 is the ecm. Note that it has an updated Part#
Physical location is under the headlight pod area.

 

THANKS MAN!!! one more question, will this module also cause it to run hot that quick?

 

Yes,especially if the fan doesn't kick on! Plus you can check under the water pump cover for any coolant leaks. There is a small weep hole especially designed to leak coolant if the water pump seal may have failed. Plus just jack the atv up in the front,wheels off the ground a little,leave the radiator cap off and see if you have any trapped air that may puge itself as the engine runs at an idle.Trapped air can also cause one to over heat before the fan is able to kick on. BUT if the hot light comes on when cold,I'd still suspect a bad ecm although you could have other issues also,plus if the fan doesn't kick on and tests good,another reason to suspect a bad ecm module..