injector tubes

i have a detroit 471. i have been getting water in the oil. the mechanic here said that it's probally a bad injector tube. how do i test to see which one? pressure test? if so what pressure does it need to be at? and how do i go about it?

First of all you do need a pressure tester. You need to plug off all the coolant passages and then apply 15-20 psi air pressure to the head and look for leaks. Now let us say you have a bad one. Replace all 4. Next you have to have the tooling to cut the inside of the new tube so that the injector tip is at the correct height. You need a pressure tester and the tooling to change the tubes and recut the tubes. More questions? It can be done on a bench but a seat & guide machine make it oh so nice.

I would start it up,warm it up,shut it off,pull valve cover,pull injectors and you can most likely see which one it is.Or you can pull the exhaust manifold and see if one cylinder is cleaner,or if you cant tell fire it up with the exhaust manifold off for a minute and the one leaking will probably be smoking way more than the others.If you find one leaking,put all of them in because the rest will be soon.You may want to look around for an exchange head somewhere,because that was a common practice at one time to just swap your head for one that had been rebuilt because there were lots of Detroit motors being used,and they had lots of cracked heads and injector tubes.Ive seen a 2 story pile of Detroit heads at a rebuild shop before,it was in Kansas City but I dont remember the name of the place,too many years,it might still be there and the price was reasonable,maybe less than what a shop would charge you to put in tubes.Sometimes the tubes wont leak until the motor is warm,sometimes they will leak anytime.Or you can use the pressure test somebody said to use.A cracked injector tube or head can cause pressure in the radiator,loosing water,if its bad enough of a leak.Those old Detroits like that,if the water pump goes out,and it gets hot,it can crack a head real easy,or injector tube,or both,usually both,or injector tubes just crack over time.