Leaky water pump

Hey,

I have a 2001 YZ 426. A bit of a new mechanic to dirt bikes, so bear with me. Last trip out last year my water pump started to leak. We decided that is was probably the water pump seal. I replaced it, and the the pump is still leaking through the hole on the bottom of the water pump. My old water seal looked just like the new one as well. Any ideas on why it is leaking and how to fix it?

Thanks,

Cory

Was the shaft all scored up? If it was you probably destroyed the new seal.

Hey,

I have a 2001 YZ 426. A bit of a new mechanic to dirt bikes, so bear with me. Last trip out last year my water pump started to leak. We decided that is was probably the water pump seal. I replaced it, and the the pump is still leaking through the hole on the bottom of the water pump. My old water seal looked just like the new one as well. Any ideas on why it is leaking and how to fix it?

Thanks,

Cory

You should have replaced the shaft and bearings along with the seal.

When I took off the cover of the water pump, everything seemed to look OK. The paddle (not sure the real name) was a bit crusty, cleaned it off and replaced the seal. I didn't remove anything else because I was told the seal was most likely the problem.

Does the shaft or bearings have anything to do with a water pump leaking? If so, how? (just curious, I'm clueless here)

When I took off the cover of the water pump, everything seemed to look OK. The paddle (not sure the real name) was a bit crusty, cleaned it off and replaced the seal. I didn't remove anything else because I was told the seal was most likely the problem.

Does the shaft or bearings have anything to do with a water pump leaking? If so, how? (just curious, I'm clueless here)

If the shaft is grooved or damaged it will not allow your new seal to do its job. Worst case with enough damage it will destroy the new seal immediately.

Yes this will cause it to drip out of the weep hole.

very common problem on the 400-426 engine. i found that even after replacing the shaft the problem would return, so u may want to replace the bearing too. I'll be honest the best fix for this problem is to put a self taping screw into the weep hole. i no people will disargee and say its the wrong thing to do etc, but i ran a bike for half a season with this fix will no problems.

Gee, that's a wonderful idea. Defeat the escape port so that leaking coolant is forced into your engine oil.

Brilliant.

:thumbsup:

Yes. I agree with that. What are your thoughts about what may be wrong?

Gee, that's a wonderful idea. Defeat the escape port so that leaking coolant is forced into your engine oil.

Brilliant.

:thumbsup:

There are a couple of things it could be. Most commonly, it's a polisned groove worn it the shaft by the old seal. This can "trap" the lip of the new seal, which, because it has no wear on it, will not want to run in the groove the old one made. That will interfere with the seal's ability to follow the lateral motion of the shaft, and keep it from sealing correctly.

Less commonly, the bearing is bad and simply allows the shaft to move more than the seal can cover.

And finally, the way the setup works, the shaft only has one bearing in the middle. One end or other has to be held in some other bearing or the shaft will be free to rock all over the place. In the YZ4**, this is done by slipping the drive tab end of the shaft into the balancer shaft, which is supporterd by its own bearing. If the balancer shaft and/or bearing gets loose, or the drive end of the shaft, or the pocket it fits in gets wallowed out, the shaft won't get the support it needs.

Thank you for your help. I won't be able to get to the bike in about a week, but when I do, I will let you know how your advice helped out. Thanks again.

There are a couple of things it could be. Most commonly, it's a polisned groove worn it the shaft by the old seal. This can "trap" the lip of the new seal, which, because it has no wear on it, will not want to run in the groove the old one made. That will interfere with the seal's ability to follow the lateral motion of the shaft, and keep it from sealing correctly.

Less commonly, the bearing is bad and simply allows the shaft to move more than the seal can cover.

And finally, the way the setup works, the shaft only has one bearing in the middle. One end or other has to be held in some other bearing or the shaft will be free to rock all over the place. In the YZ4**, this is done by slipping the drive tab end of the shaft into the balancer shaft, which is supporterd by its own bearing. If the balancer shaft and/or bearing gets loose, or the drive end of the shaft, or the pocket it fits in gets wallowed out, the shaft won't get the support it needs.

Gee, that's a wonderful idea. Defeat the escape port so that leaking coolant is forced into your engine oil.

Brilliant.

:thumbsup:

oil seal is enough to keep the water out. i no, logic says no, but seriously works with out any problem. even seen in done on crf's aswell. U are better getting the problem sorted in the long run, but it does as a quick fix.

oil seal is enough to keep the water out. i no, logic says no, but seriously works with out any problem. even seen in done on crf's aswell. U are better getting the problem sorted in the long run, but it does as a quick fix.

Experience says no, too. The lip on the oil seal faces in toward the oil supply. It isn't capable of stopping coolant from entering if the pressure against it exceeds about 2 psi.

"Fixing" it that way is like finding that your water heater is leaking and "fixing" it by locking the garage door.

One mistake on replacing the seal behind the impeller is that it is put in with the seal numbers facing out when they need to be facing in. The manual does not specify this but it is a common mistake. It will look backwards, but you are trying to keep the coolant from leaking to the weep hole that is behind the seal. Like all the ohter posts have also said, I would replace all the seals, bearing and shaft to be in the safe side. I put one of the Boyesen high flow impellers and cover. It made a huge difference when riding in the woods. I also installed a heavy duty radiator cap. Good luck!!

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