There are bunches of fiber optic borescopes available on Ebay for ridiculously low prices that will let you take a detailed look inside that water jacket. One of the ones I use regularly has a 5MM probe 24" long, a right angle mirror attachment, and a variable intensity light built in that lets me look at the rifling of gun barrels all the way down to .22 caliber, and also look inside engine cylinders. It paid for itself the first time I used it!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!