[bstark]

Mikey: Best to get in touch with the factory and ask them what they originaly used and get ahold of some then clean underside of counter and top edge of sink thoroughly to get rid of the old stuff before re-installing with new material. You will need to keep some in reserve for running a nice clean bead around inside of the joint between the sink and the counter to leave a nice clean waterproof joint.

The problem will then be how to put upwards pressure on the underside of sink assembly to ensure stable pressure while 'whatever' cures overnight. I would start by undoing the clamp ring nuts on the drain tailpieces to allow the sink to be pushed upwards without the weight of the drain pipes hanging off it and then secure it by whatever method you care to use such as pices of 3/8" lumber cut to length and jambed under the sink to force it upwards and in good solid contact with counter underside. if done correctly that should be the last of your problems with the sink as this topic has not come up before. I suspect the way they install them at the factory is while the counter is laying on a bench upside down and they simply pile some weights on the underside of the upside down sink after coating it with caulking then touch up that joint on the inside later when the counter is installed in the trailer.

The cause of problem in your case may be something simple such as not cleaning the mating surfaces of contaminants such as oil or dust. They may even suggest you use Alcohol or something like it.