My fan went out on my 98 sportsman 500 last week at Creek Bottom. I had my kids n thier four wheelers so i chanced riding mine even though fan didnt work. kept it cool by riding in creeks etc. well long story short, was on trail with no water holes and all of sudden i hear a load pop like a .22 caliber shot then i was engulfed in steam. Heard a whistling noise which was water escaping of course. Heres my dilema... Got wheeler home and started to tear down, did pressure check on radiator and could only get a leak thru weep hole on water pump. HMMMMMM i know that didnt make that loud pop! funny thing is i didnt get water anywhere else except a very slight bit of all places on my valve cover gasket????????? I have purchased new mechanical seal, oil seal, impellar, raditor, fan, thermostat and hoses...new cooling system! i drained oil and there is a slight milky to it not much...could my head gasket blow internally? what could have made that loud pop? I have the bike tore down and am going to take valve cover off tonight and check it out.... Im baffled and any help would be greatly appreciated!!

 

Sounds like a coolant hose went away to me. They can hold a lot of pressure and when they pop, they are loud!!

 

if not a hose then, i would consider the head gasket if you have water inthe oil. imo

 

metal can only take so much heat and expand so much before something gives. Hopefully a head gasket or hose is all it is and not a cracked head or block. I guess fixing that fan would've been the best route though =) "Lesson learned"

 

i have no water leaking from the bottom head gasket. i had a slight leak in radiator and water pump seal was shot!. im going to put all the new cooling items in and fire her up to see if i have anymore issues. the valve cover was loose so maybe that was oil coming out. i sure hope it was radiator seam that popped, hoses all look good.