kawasaki 700 blew a plastic piece that passes radiator fluid

Well it's not mine so I dont know all the details. Went to a friends house and he has 3 of them and offers me the newest which is a 750 and he takes the next in line which is a 700(I believe) Kawasaki prairie. Anyways we ride for a little while and we stop to talk for a second. He says that ever since he got it the temp light always comes on and has never done anything and couldnt get the dealer to fix it. Just after saying that we hear a pop like a .22 shot and smoke poors out from under him and the quad is down. We tow it back to the house and since I have mechanical background we grab the flashlight and start peaking. Well the fluid lost in the detonation was antifreeze. And the pop was a little plastic thing that appears at first glance like an inline fuel filter, but it runs radiator fluid through it. We take it off and sure enough, what looks like a 22 bullet hole right out of the bottom of that little plastic thing. Inside of it is a white plastic shaft that appears to act as a valve at that point. Now here's where natural mechanics stops. What is that thing other than a check valve? Where can he get a replacement? and has anybody had this before?