Changing the Water Pump...

There is an awful lot of water pump threads out there, but I couldn't seem to find a 'How-To' out there. I looked under the

'Common Threads: Look here 1st! Mods, Maintenance, Common Issues and FAQ's', but didn't see anything for it. I need to replace my seals and shaft and am looking for a detailed procedure as well as parts necessary.

Any help would be appreciated...


BTW, this is for an '02 426 and an '03 450 not that it should really matter, but just in case there's something weird I need to look out for....

Got a manual?

Pretty simple. Drain the oil, drain the coolant, pull the right crankcase cover off the engine. Hold the pump shaft on the inside end with a 12mm open end and unscrew the impeller. It's a normal, right hand thread, but it's typically tight.

LOOK AT THE SEALS before you remove them, and note which way they face. The bearing is cheap. Throw one in to be sure. Check the shaft for any significant wear caused by the coolant seal.

Thanks gray, I really appreciate it. I figured it probably wasn't too hard, but having some direction is always better!

im in the middle of doing mine as i type really is straight forward as it looks changed both seals and the bearing.

not put it back together yet mind there a bit of wear to the water pump shaft so was looking for a thread to see what to do about it lol.

but as i type and think the same time i guess its pointless putting it back together with a worn shaft as the seals not going to be a tite fit :thumbsup:

guess i just answerd my own question :smirk:

Its very common for the shaft to have damage from the seal. I would order a new one while your at it. :thumbsup:

The only other consideration for me was the #12 o-ring on the bottom of the radiator pipe "Y".

Having replaced seals etc.. still leaking.... on further inspection the leak was coming from around the pipe - replaced the o-ring and all is good.... had me going crazy for a while:bonk:

So I just changed the water pump parts and when I screwed on and tightened the impellar the shaft slides in and out about 1/4" before you put it into the slot.

Is that normal?

I didn't notice that when I removed the old one.

Yes. The end play of the assembly is limited by the balancer shaft, and the impeller shaft bearing.

do i need new seal after i change the bearing and shaft?

do i need new seal after i change the bearing and shaft?

Absolutely. :)

:) thanks
:) thanks

Your welcome. Be sure to check the parts diagram, but if memory serves me right, there are 2 seals in the waterpump that should be replaced. And pay close attention to the direction of the seals, they face different ways.

Thanks for all the help! Just tore it apart this weekend and it's fairly straightforward. Got it all back together and looking forward to the next ride! :)

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