it would have a crack with water dripping or spraying out of it.
The first thing to look for would be an exhaust leak. Check for a fuel leak on the top of the engine.
You have a water leak. Look for a trail from where it is entering.
well you look up from where the leak is coming from or the wear the water is dripping from and their you go you fond out wear the leak is.
One way would be to fill the tube with air, and then hold it under water and look for bubbles. Wherever the bubbles are originating from on the tube is the source of the leak.
It would look dead.
A roof leak will only be around when it's raining and a plumbing wall leak will be there forever. Which do you have? Food coloring in water and poured down suspected leak paths is very useful. Use different colors.
Unless you dug the whole line up you probably wouldn't find the leak unless it was a very large leak which would bring the water to the surface, You would be better off just installing a new line. Call a leak detection company. They will find your leak to within inches, and you will be able to dig down, repair the line where it is broken, and repair it.
There are many possible leak points, but the most common place for a trunk water leak in a neon is around the tail lamp mounting bolt holes. If you are unable to locate and repair the leak, there are people who specialize in this type of repair.
They would look for things like natural gas, radon, and propane. They may need different equipment for different substances.
Heater core
To find water bottles that don't leak, look for bottles with secure lids and seals, read reviews from other customers, and consider brands known for their leak-proof designs.
Milky oil is oil with water in it. The water is usually coolant. Common causes are failed headgasket, cracked head, internal leak in an oil cooler.