water pump seal installation

3 replies to this topic
  • Speedracer747-400

Posted August 06, 2002 - 09:33 PM


I'm installing new water pump seals in a 98 yz400. The manual says to install the oil seal with its manufacture's marks or numbers facing inward. Do they mean both the oil side seal and water side seal get installed this way? Funny thing when I took it apart the oil side seal next to the bearing had the markings facing outward. Did Yamaha install it wrong at the factory? Thanks for the help. :)

  • Rich_in_Orlando

Posted August 07, 2002 - 04:50 AM


Let's see if I can muddy the waters a bit.

The two seals have a smooth, flat side and a side that's ridged. (That's the best way I can think of to describe it from memory.) The ridged side has a little metal band imbedded in it that helps creates the seal. That side needs to be in contact with the fluid. The smooth sides need to face inwards towards each other. The "inside" is actually the "outside" (leading to the weep hole.)

When I replaced the water pump seals on my '99 WR, I neglected to replace the shaft. It leaked even with new seals, so I had to do the job a second time, this time replacing the impeller shaft and the seals again. Check the shaft condition carefully and if you see any wear, replace it.

[ August 07, 2002: Message edited by: Rich in Orlando ]

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  • Hokie

Posted August 07, 2002 - 05:04 AM


This won't help with your seal problem but...

Be VERY careful when putting the oil line bolts back in. You don't want to strip the threads out of the soft engine cases.

Don't ask how I know this......

  • humbertob

Posted August 08, 2002 - 05:27 AM


I have installed the oil seal, coolant seal and bearing of the water pump on my '99 YZ400 weeks ago and the only part that must be installed with its manufacture's marks or numbers facing inward (to the engine) it's the Bearing itself, the seals must be installed like "Rich In Orlando" already wrote here ! Mine was letting escape coolant from the weep hole and this cured the problem totally ! Good Luck ! :)

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