Coolant system question

[.Holdon.]

hey, how does the coolant system warning light know when to come on. does it measure the pressure level in the system; so if theres a leak the pressure will drop and the car will know the level is dropping?

cheers

[BlackVT5.7]

From what my VT has, it comes on when the level drops in the reservoir bottle.
There is a sensor in the base of it.
You could assume this is carried on until the VZ's when they did away with the reservoir.

*edit* Just to lead on from this, if you have noticed a drop in your levels, check the plastic end cores of your radiator for leaks, extremely common. They tend to crack around where the hoses connect to the top/bottom of the core.