I tried the 3M fast and firm seam sealer and this stuff sucks. After 2 weeks in the florida sun every section I applied it too cracked and had to be removed, doing things twice is worse than doing it the first time, it didnt seem to matter how thin or thick the application was. The same thing happend with liquid nails which was kind of a long shot. The only decent thing I found was JB weld. I did the entire drip rails in this and so far its been fine. Primer seems to hold to it real nice and its been baking in 92 degree florida sun with no problems. Just thought I would share and save someone some time who planned on using 3M fast and firm
Did you apply the seam sealer over bare metal or primer? We use 3M seam sealer all the time and it doesn't crack because we prime the area to be sealed first.
Jean, do you know why the primed section doesn't crack and what type primer are we talking about. not that i would put any primer on my car, this is just for the ones that my be getting a car ready for paint... ...Frank...
I used a base epoxy metal primer, then urethane primer over that. Then I applied the 3M Fast-n-Firm. In all locations, trunk, door jams, drip rails, the sealer cracked after 7 days and cracks grew larger by 14 days. The cracks are small and hard to notice at first but you can see them when you inspect them closely. Also note that you can not see the cracks in section that I have primed over the sealer. I believe that the 3M product is a laquer base system and keeps shrinking over time. My concern is that the cracks will become larger as time gos on. Which leads me to think that any time your doing a show car quality paint job that a 2 part sealer that uses a hardner will work much better.
