whats causing my coolant leak?

I recently purchased an 05 yz450f and have been riding a few times on it. Yesterday my buddies and I went on an all afternoon ride. My buddy was riding it to test it out and when he came back to talk to me there were a couple drops of antifreeze on the floor under him and a little on the edge of the case by the outer case seal on the right side. We didnt think it could be overheating becuase he was doing highspeed runs down the road. After letting it cool a bit I was riding it for a bit and when I parked it there was decent drip rate of coolant coming from the water pump area. I immediatly rode it to the shed and parked it to prevent any further possible damage. My question is what could be happening to cause this coolant leak. Thanks much for any help and sorry for the long post.

its the impeller shaft seal, mine was leaking and i just replaced the seal and it stopped. just makes sure the impeller shaft looks good, or u will have to replace it.

thanks I'll have to look into it more when I have time off of school.

its simple to change the seal

Since I dont have my manual yet, is that just the seal on the cover or a seal inside there so that I need the cover seal and another one?



Now you have a manual.

The impeller cover seal itself is a shape-formed "O" ring, and probably will not need to be replaced.

However, while it is possible to replace the coolant seal on the water pump simply by removing the cover and unscrewing the impeller, it is not at all advisable. First, this action subjects the drive tab of the shaft to the torque load of breaking the impeller free, which can be quite high, and the shaft may well break. Secondly, the impeller shaft has about a 75% chance of being worn badly enough that the new seal will either not hold at all, or will fail shortly after replacement.

The correct procedure is to drain the coolant and remove the right crankcase cover. The shaft has a pair of flats ground on it that allow it to be held with a 12mm wrench while removing or retightening the impeller, and with the case removed, the oil seal can be replaced at the same time, and the shaft can be more accurately inspected.

Don't cut corners.

i replaced just the seal and its lasted over 6 months so far. but it all depends on the condition of the impeller shaft good luck:thumbsup:

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