Rubber shock tops

[gazza1701-a]

I have water seeping through the rubber shock stopper/tops on the rear of my cav, seems like water is getting splashed up off the wheels and works its way between the rubbers, the shocks are after market ones not GM and about 18months old, rubbers aren't split or cracked, i did try tightening them up to see if that would compress the rubber a little but they felt tight enough, so anyone else had this problem? Can you buy just the rubber washer type things from Vauxhall ?

[Super89]

Dont think they are available anymore, Took GPS awhile to find me some. Could try some sealant?