water pump FZR250, but general advice needed, probably.

[KevTM]

I noticed water coming out of the water pump housing a few weeks back after i revved the bike to 18k for the first time (not had the bike long), it wasn't leaking water for the 450 miles i done previous to this sitting at around 10k.

Anyway i replaced all the water pump seals, filled up the cooling system etc again ran it at idle for ages, no leaks, perfect i thought, so i took it around the block and again for testing reasons took it to the redline and again water started coming out of the hole in the water pump housing.

At the engine side of the pump working the way back, there's:

Circlip & washer (to hold propeller in place), bearing, oil seal, then the section of the housing where the hole is, then the mechanical water seal (it has a large spring in it), then another seal inside the plastic propellor.

Once assembled in the housing the propeller can be pushed in (and gets pushed back out due to the large spring) so i'm wondering if there's maybe too much pressure in the system (i.e. a blockage somewhere) would the water build up enough pressure in the pump housing to push the propeller shaft in to allow the excess water/pressure to escape through the hole to prevent damage to any other parts?

Does that seem likely? or is this how other pumps work or not i have no idea.

thanks for the help

[Paddy Blake]

If you were to redline it in gear then it would have less built up pressure
in the housing.So fix it and don't redline it when not in gear as the pressure builds up fast in the housing and has no time to go trough the system.
If you rev it gradually the system has time to let the coolant flow.


Paddy.

[KevTM]

well i never tried redlining it out out of gear but your post is confusing to me, seems like you first said revving it in gear has less built up pressure, then revving it in gear has more built up pressure?

[KevTM]

yeah cool paddy, cheers.

well even though i tested the thermostat in boiling water and worked ok i decided to take it out to test it as the guage wasn't going up even though the housing was roasting... took it out and it seems to be ok so far

i'll keep it going just now without a thermostat just to make sure then i'll order a new one for it.

time will tell.

[Paddy Blake]

Sorry about that I only had time to edit my post on my 30 min lunch
break.
The rad cap should release the pressure way before it will blow the seal so
I would check that it has the right rad cap.I have seen race bike come into
the pit with water pissing out of the rad cap and no seal were damaged.
I wish I could be of more help but that's all I can think of for now.
Did you grease the seal and shaft before putting it back together.

Paddy.

[KevTM]

yup,

it appears to be working ok now that i removed the thermostat maybe it's a bit dodgy, it did open in a pot of boiling water though and i have let the temp increase quite a bit so hopefully that's all it is.