They are cheap enough that they are worth a try. As AcuraTech mentioned, cleaning everything really well and watching for leaks should be the first attempt.
Another way to look for leaks is a clean spot where everything around is dirty. Coolant leaks will often show up this way.
Every once in awhile a dye kit will save your butt. Usually they aren't needed.................until you need it. I had one oil leak that turned out to be caused by a bad block casting (porosity) that almost killed a paycheck. I would have never found it without that UV dye. If you do use UV dye, get a little AA/AAA flashlight with a UV LED. It is a great timesaver and fits everywhere larger lights don't.
I have a coolant leak on my Dad's Caravan that never shows any coolant leaking anywhere.
I will try harder to track it down this weekend. If unsuccessful I might buy a leak kit. I do notice that the system is not pressurizing, so the rad cap is one of the first things I am looking at. It was replaced a year ago though.
Thanks for the input.
I don't think you need UV dye in coolant. I find that the black light lights up coolant the same as a fluid with UV dye in it. This cause me all kinds angst once when I was looking for a possible a/c compressor leak, and the clutch was sitting under the water pump weep hole.
You can pressurize the cooling system thru the overflow tube. Easiest done with compressed air and a pressure regulator set to about 13psi. Very useful for detecting cooling system leaks.
Yes this is what I have done before. I had a little black light for pet accidents. It up and vanished. I notice the system is not coming up to pressure as well. The cap is one years old. I will try the cap off another vehicle.
I think I will pressurize it and see if I can find a leak before I worry about chasing things down with a black light.
I used the dye to find a water pump leak before. I also used a $8 actinic bulb (for marine aquariums) and installed it in a $6 portable fluorescent light fixture. It's brighter than those LED pens. A black light would work fine too