He drools when you pet him right
My cats do that too, they also drool in two specific circumstances even if you aren't petting them.
One, the gray cat when you are holding her and your hair is long enough to stick her face in, she'll drool in your hair. No petting really required.
Two, if the tabby is in your lap making biscuits she drools. Sometimes she'll make a little slurpy sound first like she's trying not to.