I want to do an intake leak test and the service manual says to use propane to do it. It says if there's a leak then the tone will change. What kind of bad consequences can result when propane enters the engine?
I'm thinking that since it's the intake manifold, if you use a spray bottle and spray water in the intake manifold area, if there is a leak, you'll hear a definite difference in how the engine runs. Same same with WD-40. Or as Ross Perot used to say about Washington, you hear a giant sucking sound.
I would def use something that is non-flammable. Water would not be a bad choice at all. When you spray the water onto the intakes, the idle will change if there is a leak.