coolant loss all at once

[winrock]

car is not overheating while driving,, but the last couple a weeks 3 times after driving, severe coolant loss , . cant find where it comes from, and of course when i watch for it , all is fine . Happening as car is cooling down , seems to lose a half gallon or so. any ideas ?
thanks

[newscarver]

a pressure test will find most leaks...that are leaking to the outside anyway

[aarcuda]

check to see if your oil is grey? if so, you are dumping it into the engine block.

[winrock]

oil is fine ,, coolant is going on to my driveway,, and well so is some oil

[fltstn]

Check your coolant cap. I lost my coolant anf found my cap messed up. I replaced it and so far no more leaks. Good Luck...