Originally Posted By: Chris142
Nothing. When the paper gasket gets wet it will expand some and form a tight seal.
[Lumbergh voice]Um, yeah, I'm going to have to disagree with you.[/Lumbergh voice]
If it's a good quality paper gasket on a nice, new flat surface- then I'd agree with you. But when we're talking about thin/cheap aftermarket paper gaskets being used on old, pitted, less-than-perfect sealing surfaces... you'll likely have problems if you just put the gasket on dry.
IMO, it isn't that critical just what type of sealant you use- as long as you put SOMETHING on the gasket to fill in the imperfections (coolant is thin and tends to look for a way out). I've used silicon, anaerobic sealant (loctite 504, 555 or the like), aerosol hi-tack, aerosol copper hi-tack, 3M weatherstripping adhesive, permatex #2, aircraft gasket dressing, spray paint, Indian Head gasket shellac, hylomar... probably a few others. All with good results.
Of all those, I probably like aerosol hi-tack the best. It sticks the gasket in place nicely, helps it seal, and is easy to apply. But it tends to make an overspray mess. None of my concern- but some people care what an engine looks like.