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Is there a rubber O ring in GTS 300 Expansion tank plug/cap?
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@melt avatar
melt
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Vespa 2013 LX125, 2017 GTS300
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melt
Enthusiast
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Vespa 2013 LX125, 2017 GTS300
Joined: UTC
Posts: 96
Location: London
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My GTS 300 weeps a bit of coolant from the expansion tank plug/cap part number 623673.
I can't see a rubber O ring. So what seals this?
It may also be the expansion tank has a tiny split I can not see.
Its not much but its there.
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jimc
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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jimc
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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Yes there is a flat rubber seal - right in the depths. Hard to see, but you can feel a bit of 'give' when it's prodded. I'd be very, very surprised to hear one had magically vanished.

The cap should seal (IIRC) up to 3bar (~44psi) then release excess pressure.

I've had two expansion tanks give way on me. They tend to split at imperfectly joined seams.
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@melt avatar
melt
UTC
Enthusiast
Vespa 2013 LX125, 2017 GTS300
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Location: London
 
melt
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Vespa 2013 LX125, 2017 GTS300
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Location: London
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Thanks Jim. There is a rubber gasket in the tank cap but I'm guessing the rough edge on the left doesn't help. Looks like someone has had a nibble! Why would anyone do that!
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jimc
UTC
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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Location: Pleasant Hill, CA
 
jimc
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@jimc avatar
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 46117
Location: Pleasant Hill, CA
UTC quote
That blemish won't help the seal, for sure. A new tank is ~$50 before taxes and shipping... so I'd experiment with very gently filing down the roughness with a fine file, and maybe using some thick PTFE tape to wrap around the threads just overlapping the top edge.

A new tank is the best solution though.
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