WR 400 water pump leakage

5 replies to this topic
  • darby73

Posted April 17, 2007 - 07:26 PM


I started my wr400 up this spring to find that coolant is leaking from the hole on the bottom of the water pump. I have flushed the coolant system and retightened all bolts to ensure nothing was loose. I have never taken off the water pump so the seal shouldn't be in backwards, as I read somewhere that that could cause this type of leakage. I have had the wr400 for 3 years now, and it is a 1999.
Any suggestions?? :thumbsup:

  • motorcycleman

Posted April 17, 2007 - 07:49 PM


You will need to replace the seal, the bearing, and probably the shaft. I was able to polish the shaft on mine and save it. (The seal wears a groove in the shaft.) Its a common thing to happen and an easy fix.

  • motorcycleman

Posted April 17, 2007 - 07:57 PM


Correction: I think it has two seals.

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Posted April 17, 2007 - 08:02 PM


Unfortunately you must remove the right side case to hold the shaft to remove the impeller and replace the two seals and bearing. Check your crank seal while your in there. Mine was in bad shape on my '98.

  • scott_h

Posted April 19, 2007 - 09:16 PM


It's not hard to fix. Remove the clutch cover. This will allow you access to remove/inspect the impeller shaft and support bearing. The shaft will sometimes become corroded or worn resulting in reduced seal life. Also, while you have it apart, be sure to replace both seals (the outboard seal keeps the coolant from entering the gearbox while the inboard seal keeps the gearbox lube from getting into the water pump). Check the Yamaha website http://www.yamaha-mo...parts/home.aspx for an exploded diagrams and part numbers to save time. If you don’t have a service manual – get one. Good luck.

  • darby73

Posted April 20, 2007 - 09:27 PM


Awesome.. Looks like I have a project for tomorrow. I just hope my local Yamaha dealer has the parts. I started it this afternoon to just let it warm up, and after about a minute I noticed the header, just off the cylinder, was glowing red. Looks like I may have to clean out my carb too. This will be another first for me.. fun fun fun


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