How to re-seal a car body seam?

snipped-for-privacy@aolbin.com brought next idea :

Capt Tolley's creeping crack cure might be a way forward, it wicks itself into a narrow gap.

In message , Harry Bloomfield writes

My Focus Mk1 boot is leaking at both sides. Of course, the tail lights are the usual suspects - but tests seem to indicate that they may not be. I've got duct tape over all the possible areas of ingress - plus over where the rear quarterlights meet the body. I'm now working on the bottom (where the rear bumper meets the body).

However, I had my eye on this sealer in case I need it (but haven't got any yet):

Thanks, from a quick look that seems worth a try

I've had a hell of a job finding the problem. I used plumbers mastic to blank off different areas and build barriers - starting at the bottom with a hosepipe and working up as each area could be ruled out.

Just had a look at your link - it's silicone!!!! Don't use silicone if you might want to paint afterwards.

I shouldn't think I will be - but advice noted,

There are pukka car seam sealers that can be painted over - which I doubt you could do with a mastic.

Hmm the problem then sounds like faulty manufacture. Trouble is that rust has probably already started and with expansion and contraction and vibration its going to be a big problem to keep it sealed. Is the car very old? These things used to happen a lot many years ago but modern cars joints are a lot better.

Brian

seam sealer did it to my Dacia Duster .......