bad thermostat?

Hi guys, doing a bit of electrical work on my 2006 450 EXC today and had the bike idling for about 5 mins as I tested some of the electrical outputs.. anyways after about five mins the bike began spewing out coolant from the hose that goes into the thermostat from the water pump, why would this happen? It was almost like it built up pressure behind the thermostat until it started coming out. The hose stayed tight on the thermostat and seems to still be sealed. Makes no sense to me. It was only about 5 degrees outside when it happened. Any input?

This doesn't make any sense to me either. After idling for 5+ mins, without a fan, the engine will be close to overheating. Are you positive that the coolant isn't somehow coming from the overflow tube? Or perhaps the plastic thermostat is defective?

Replace your Thermostat. KTM Thermostats have been know to go bad......

This doesn't make any sense to me either. After idling for 5+ mins, without a fan, the engine will be close to overheating. Are you positive that the coolant isn't somehow coming from the overflow tube? Or perhaps the plastic thermostat is defective?

It makes sense that the bike got hot, but I'm pretty sure that it came from the hose going to the thermostat.

We had one of these where the hose had a very tiny hole in it, under the hose clamp. It would only lose coolant when the bike got hot. It took a long time to ever find the problem because it would evaporate off when riding and never show a sign of loss.

I would check the location the coolant is coming from from a problem before assuming there are issues.

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