GTS water pump seal replacement
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GTS 250
Joined: 26 Apr 2008
Posts: 240
Location: California
Fri Mar 15, 2019 7:12 pm quote
After searching all over this forum & the internet, I was unable to find the correct Piaggio water pump seal drift that would allow setting the seal correctly.
A custom machined (not available) drift can be seen here

For those who don't know, the seal has a tension spring and needs to have the outer half and inner half pressed in place at the same time but at different depths. You can't just drive the outer half only without destroying it. The spring needs to be able to compress in the drift without bottoming out. The seal is very fragile, and I destroyed one before I came up with the method below.

I found a 1 1/16 socket worked good for the outer seal. Two washers & a plumbing fitting are used to take up the height difference for the inner seal. Any parts can work, as long as the heights & diameters are somewhat correct.

The assembled makeshift drift.

The seal, sitting in the drift ready to be pressed into the waterpump housing. The spring can compress, but not bottom out (roughly 1/16").

Molto Verboso
Vespa GTS 250ie
Joined: 02 Jun 2015
Posts: 1218
Location: San Francisco Bay Area
Mon Mar 18, 2019 9:34 am quote
Nice, lateral thinking there!
GTS 300, BV250
Joined: 29 Jun 2018
Posts: 53
Location: Orange County, CA
Sun Apr 28, 2019 9:17 pm quote
I've been holding off doing this because of this 'special' tool as well...

I saw your solution and went looking for a suitable socket. Couldn't find one but I was able to scrounge around the garage and come up with another alternative, this one cast in plastic.

Behold the PVC Water Pump Seal Tool (PVCWPST)!

I fashioned it from a 3/4" union with a bit of 3/4" Sch 40 PVC jammed in one end to approximate the correct spring plunge depth. Another, longer piece got stuck into the other side to serve as a handle. It took a few attempts at cutting the PVC to get it to where the depth seemed about right. A few gentle taps was enough to get it most of the way in. I had to spin it around a few times as the cut wasn't quite square.

I won't know if I destroyed the seal until I get some coolant and fill it up but it looks like it seated properly in the cover. There's resistance to turning the shaft but nothing feels broken.




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