Water Pump Questions on my 99 YZ400

My Water pump has been leaking out of the little hole on the side of the water pump. All the research I did on this great forum led me to believe the seals on the impeller shaft need to be replaced.

My questions are...

1. Do i need to take off the right crank case cover to replace the inner oil seal or can I access the seal by only taking off the water pump cover off?

2. How do I know if the oil seal needs to be replaced?

3. if those seals need replacing, Should I also replace the impeller shaft???

Some quick help would be great be cause I got all the new seals in my hand and I would like to do all the work tomorrow.

Thanks for all the help Thumper Talkers!!!!!:applause::excuseme:

Patrick M.

1> No. The inner, or oil seal is only accessible from inside. And you should also never attempt to replace the outer, or coolant seal without removing the cover, either. Enough force is required to unscrew the impeller from the shaft that there is a very real risk of breaking the drive tab off of the shaft in the process. By removing the cover, you have access to the flats ground onto the shaft for holding it with a 12mm wrench. Do it right.

2> If the oil seal were bad, it would be leaking oil from the same hole it is now leaking coolant from. The seal is cheap, and you're going to be in there, anyway. Just replace it. That way you won't have to do it again when you find out how long they last after the coolant seal fails.

3> The shaft may have a groove worn into it by the original seal. Don't confuse this with a groove that is deliberately cut into the shaft. It won't look like machine work. If the groove is deep enough to feel, it will probably cause the new seal to fail almost immediately. Also replace the bearing if it feels rough or excessively loose.

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