please forgive me because I'm a novice at this, but is that safe to do? It sounds kind of dicey LOL

 

It won't make enough pressure to hurt anything. Pull the truck outside and place the vac in the bed so it directs the sound away from you and get some cardboard to slide around on. I would also look around for any soot on your exhaust pipes. This is indicative of a crack.

 

Lol, I'm sure you can handle it. It's an old trick of the trade of sorts. Guess you have to do it once to make you a believer. Anyway, if the hose don't quite fit, pack rags around it lol. If you have an air compressor, regulate it down to 15 or 20 psi and again use a shop vac insert/reducer. This has been done for as long as I can remember. Squirt bottle with dish soap and water mix. You don't need much dish soap...dawn works well. Turn the vac on, get yourself under the truck and hit the seams w/squirt bottle.

I've done this along with others to check welds and header gaskets.

CAUTION: Wear safety glasses to prevent bubbles from exploding in the eye sockets....that's a stinger. Might better keep your mouth shut as well while preforming the procedure...it's distasteful.

Have no fear and good luck.