I've had a leak on the back box on my Volvo V70 for the last few years. Every year I bodge it up with Gun Gum for the MOT but it doesn't last long before the dry putty gets blown out again. MOT is due again in next few weeks and I want to see if I can make the bodge last a little longer this time (eventually I'll be getting a full SS system but funds won;t allow it at the moment).
This pic shows the type of box and where it's blowing......
...it's double skinned and the top skin has rotten through and I've pulled half of it off. The actual leak is at the seam where the top and bottom half of the inner skin have been pressed together. I usually just work the Gun Gum in around the lip and that is good enough for a temp seal.
Are there any better products to use than Gun Gum? I was thinking possibly use the Gun Gum to form the seal, then after drying put a layer of P40 glass fibre over the top as it's pretty strong stuff (and since it's the back box and I don't drive the car hard it doesn't get stupidly hot). It would be hidden from view once back in place.
(*respecting the fact that this is just a short term repair, and just needs to seal and hold and not look pretty)