Losing Coolant! Help Please!

Traded for a 2006 YZ450F, Got home, rode it for bout 5 mins and it quit...w ended up putting an o-ring on the metal tube that runs frm th radiator hose setup into the top end. filled it up with coolant. Went and rode and it leaked bad out of the weep hole. We rebuilt the water pump, Seals, bearing, shaft, not a new impeller. filled it up with coolant, rode....but....it would get hot, as normal, then start acting up and missing, eventually, it will bog down like im running out of gas. i can set there for a little while and let it cool down a little bit, then ride for a few minutes longer, but it does it again. i got home and looked in the radiator and it was empty. Well, i say its empty, i cant see any in it. it doesnt blow white smoke out the exhaust, and as much as i can see from the dipstick, there isnt any water in the oil. Wheres my coolant going? Also, would the oil be milky with Engine Ice in it? Me and my dad are lost! :)

There's only three places for it to go. Out the exhaust, in the engine oil, or on the ground. You say there's no smoke which is good, now drain your oil to be sure it's not in there. Sometimes a radiator cap will stick and over-pressurize the system, forcing it to blow the water pump seals again. Maybe stick a small piece of tissue in the weep hole and then inspect for fluid.

Yes, if coolant was in the oil it would be milky. Head gaskets are not normally a problem on the 450 unless the head was removed and improperly torqued.

You could have installed the water pump seals backward (a common mistake). Read:


Or you might have a little bigger problem:


The problem with how it runs hot might also be an unrelated electrical problem with the stator.

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