I'm not sure if it's my radiator or the cap. Problem 1, didn't overheat, but antifreeze came out the top of the radiator, where the plastic top meets up with the radiator fins. Replaced the radiator, with a used one, didn't have any leaking at first. Then machine warmed up real good, and started leaking in the same place. Is my radiator bad or does the cap need to be replaced. Doesn't seem to be leting the excessive preasure out. Thanks all!!!

 

mine leaked and i thought it was the rad but it was the temp fitting screwed into the top tank that was loose.

 

I have had the same problem with my '99 Sportsman 500 for two years now. It only seems to happen when the machine is sitting idling for a period of time right after start up. I took the radiator completely out and had it pressure tested, no leaks found with the factory cap installed. I started thinking that the over flow tube was seeping coolant but I wasn't sure because I could never see it leaking. I replaced both radiator hoses and installed new clamps. The thought of the temperature sensor leaking hadn't crossed my mind (didn't see any sign of leaking) but I will check that next. The leak seems to go away after the bike is warm and I start riding it.

Gsport500

 

I thought it might be that sensor also, but it's not. After talkinng with the dealer, he thinks that it might be the head gasket, causing excessive preasure in the radiator, this in turn causing it to leak out the seams, which under normal preasure (13 lbs) it doesn't leak.

 

Problem fixed! The head gasket, which was new not 30 hours ago, lost the inner ring. This caused the exhaust gases to go into the water jacket, causing excessive preasure. It didn't pull any water in though, almost acted like a one way valve. If anyone is interested, it was a "Moose" top end kit that WAS in there, went with a different one this time. Thanks for all the ideas people!

ProX