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SmallMonkey

WR400 Coolant leak

10 posts in this topic

Hey all, I just noticed a small Coolant leak on my 400. It seems to be coming from the water pump.

I have not hit anything or taken the cover off - Nothing that might tear the gasket. The leak looks like it's coming from a small weep hole (a hole on the underside of the water pump cover), but I don't think that my bike has a weep hole.

Any ideas? Thanks!!!! :)

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Time for a new impeller shaft and oil seal and water seal pretty easy to do.

Do you have a service manual if not GET ONE! they are about 30.-40 and are worth the money .In time you will if mechanically inclined be able to do a lot of the work on such an easy motors to work on. :) and if that does not work than you can always ask a question on TT and of course get an answer :)

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Moutainrider is right. If it's leaking out of the small hole under the pump, it's time. Yamaha put that leak spot there just for that warning. My 98WR never did that, nor the 02WR, just the 03WR - after two years. :)

I run Blue Ice in the coolant with some Redline water wetter. Thought that issue was history. Not. Must be lack of true specification at the factory. :)

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OK, I see everyone recommending a new shaft plus seal whenever the water pump leaks. I developed a leak on my 04 WR with 90 miles on it. I just replaced the seal itself and the leak is fixed. I supposed I'd check the shaft for a groove, if there is one, either install the seal a little deeper or maybe even shallow so the lip rides in another area. Then replace the shaft when its all grooved beyone repair.

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MDT, you got any theories on why this happens? Seems something like a shaft and seal should last at least as long as other major engine parts. Could it be the quality of the coolant? If so, what would you recommend, stock or aftermarket?

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MDT, you got any theories on why this happens? Seems something like a shaft and seal should last at least as long as other major engine parts. Could it be the quality of the coolant? If so, what would you recommend, stock or aftermarket?

No need for theories! The water pump seal has no lubrication and runs dry on the shaft except for coolant that may get in there. That is why the shaft wears and the seal wears out quickly. Once a year replacement on the WR450's. :)

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No need for theories! The water pump seal has no lubrication and runs dry on the shaft except for coolant that may get in there. That is why the shaft wears and the seal wears out quickly. Once a year replacement on the WR450's. :)

Another theory is that dirt can enter through the weep hole and cause premature wear. One TT'er suggested putting a dab of grease into the weep hole that would help keep dirt out, but a bit of pressure from an oil or coolant leak would displace it and let it do it's intended job.

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