AC was on?

 

With high probability the condensation water of the air condition. And this would be completely normal. Have a look under the car, there is a small hose which dissipates the cond. water.

 

Does it have any colour? If not, it's almost certainly nothing to worry about.

Don't open the coolant system with a hot / running engine - it is a pressurised system. You should also use the correct coolant, not water, and certainly not tap water (if that's what you used). A small amount shouldn't hurt though.

 

ac was off,

 

sure it was not from ac, it was water with antifreez, and it was not small amount,
it tooks 2 liters to refill, so stopped 3 tomes to arrive to mclaren service adding water,

 

Ah. Glad that you know what it was. If it didn't overheat, it shouldn't have done any damage, and (as has been said) is probably just loose clamps.

 

Probably a loose water hose clamp, it is a known Problem. I have replaced at least 70-80% of all clamps.
Shouldn´t be a big issue, depending on where the hose is leaking.

 

It's doubtful there is any damage however depending on the head design low coolant can cause localized hotspots that might not get picked up by the coolant temp sensor. Had a car where this occurred, the head shifted slightly and tore viton (sealant layer) off a MLS headgasket. In this case 2 liters seems like a relatively low amount of coolant to be missing, about 10% so it's probably fine.

 

i hope it is not a big issue, anyway extended warranty does cover such issues?!
tomorrow they will call me to report the problem , i will let u know
thx guys

 

problem is solved, c pipe for cooling the clutch.