Over heating problem

If you're referring to the little hole down at the bottom of the impeller in the crankcase cover (not the water pump cover), no that is not normal except to say that your water pump seal is gone. Plenty of posts to tell you what to do from here, just do a search. I just replaced mine but I did both inner and outer. Most people will tell you to just replace the outer which is much easier and less involved. Mine's a '98 so I wanted to upgrade to the '99 shaft anyway. Good luck.

Originally posted by zack_attack190:


Bingo! Your outer impeller seal is shot. It is very easy to change though. Unless you have water in your oil, you only need to change the outter one.

See ya,


I have a 1999 YZ400F, last saturday, I noticed

radiator fluid come out of the little hole on the

impeller cover. Is this normal? It was very hot

near 97.

I then checked the level and it was down. Any suggestions?



It will be better to replace the inner and outer seals, and if you can afford you must change the water pump bearing, I already replaced them weeks ago and the total for parts was only 33.00 dlls including shipping and handling at www.Ronnies.com the process to replace both seals (inner and outer) and the bearing is so simple, but I recommend to disasamble your bike before you get the parts, check the impeller shaft and if it's shoted, replace it also. Here are the step to change the seals as well as the bearing.

1. Remove the frame bolt to let the oil go out form your bike

2. Remove the engine oil bolt

3. Remove the Header Pipe

4. Remove the Brake pedal (Don't forget to remove the clip that it's behind the pedal bolt)

5. Remove the kickstater

6. Remove all the screws that are around the clutch cover and remove the clutch cover itself

7. Remove all the screws that are around the right crankcase cover.

8. Remove the banjo bolt that is over the top of the right cranckcase cover, be careful with the washers that will come off the bolt.

9. Remove the oil line that is under the bottom of the right cranckcase cover, be careful with the dowel that will came apart when removing this part and save it for reuse it.

10. Now you can remove your entire right canckcase cover, be careful with the 2 dowels that will came off from the right crankcase cover.

11. Remove the bearing with caution using a screwdriver, try not to damage the housing with the screwdriver.

12. remove the inner seal using the screwdriver and with caution, you can use a rag to use it as support and not to damage the housing.

13. remove the outer seal using the screwdriver the same way you removed the inner seal

14. apply white lithium grease on the lip of the outer seal and install it

15. apply white lithium grease on the lip of the inner seal and install it on the bottom of the housing.

16. apply white lithium grease on the lip of the bearing and install it on the top of the housing taking care not to damage the housing.

17. Now install the Impeller Shaft and you are done, the installation process of all the other components are reverse of removal.

18. Make sure not to over-tight the clutch-cover screws and the right cranckcase cover screws as well, if you can replace at this time the clutch cover oil seal and the right cranckcase oil seal as well, if both seals are not distorted you can reuse them, I did !

If you can use watter-wetter in your radiator it'll will be pleased with you, I'm using it with great results.

Good Luck !

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