Water/Coolant leak need help?

Hi there just to go riding today and when i checked coolant level on my 01 YZ426 I could not see any water in the rad at all so I poured distilled water in the rad and noticed that as I poured water in it was coming out almost as fast at the bottom of the water pump housing. Now it is coming out of the small hole at the bottom of the water pump. Never noticed this before is there supposed to be a plug of some sorts or any awnsers would be greatly appreciated.

thanks ahead of time.


The water is supposed to run out that hole when the water pump seal fails, because it's better than having it run into your oil.

You need two seals, and probably the shaft.

It sounds like you are referring to the drain hole in the bottom of the waterpump cover. This is where you normally drain the water out of the bike if you need to do engine work. There is supposed to be a bolt in it plugging the hole.

So all i need is the 2 oil seals why would the shaft be bad? sorry don't want to sound stupid is there a way to check the shaft?


The shaft gets worn by the seal on the water side. Coolant is a much poorer lubricant than oil, and the seal will actually wear the shaft enough to keep the new seal from holding. The only way to check it is visually by removing and inspecting it.

The bolt KJ is referring to is the lowermost water pump cover bolt on the side of the case. The escape hole is the one under the water pump that can't be seen except by looking underneath the pump.

Dont forget the bearing. If its worn at all it will allow the shaft to wobble and leak past the seals.

While the bearing is important, no shaft is ever fully supported by a single, single-row cartridge ball bearing. There are always two points of support where such bearings are used, and in the case of the water pump shaft, the second point is the fit into the balancer shaft that drives the pump. The bearing itself is rarely the cause of leaks, although it isn't terribly expensive, either, and on an old bike, you'd as well replace it.

But that also means you need to check for looseness between the shaft and joint, and within the balancer shaft bearing when doing this job.

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