: WD-40 is a water-displacing spray originally designed to repel
: water and prevent corrosion; WD-40 stands for "Water
: Displacement – 40th Attempt" according to Wikipedia.
: Don't see why it wouldn't work if the piston to cartridge line
: was completedly covered.

The thing is that once the seal is broken a bit of air has already worked its way past the plunger and into the tube and that air will tend to set off the sealant.

Most of these sealants you can buy in smaller tubes, if you don't need a large amount it's just easier to buy a smaller tube and toss what you don't use.

Bill H.