How do I seal a joint that will be immersed in water/oil/coolant?

We typically will want the sealant to be fully cured before being put into service in these types of conditions. Proper surface prep will help create good bond strength and a good seal. We recommend solvent cleaning with 3M™ Adhesive Remover or methyl ethyl ketone (MEK). Do not use isopropyl alcohol to clean when using an adhesive sealant. For increased bond strength, you can abrade before cleaning. There are also primer options available that can be used after cleaning. Our 500 series Polyurethane Adhesive Sealants work well for these conditions but if you have harsher chemicals we suggest only occasional splashing and not total immersion.