My car started overheating after several weeks of not being driven. Filled radiator, seemed fine. Didn’t drive at all after that for a week or two. Wife drove the car today 30 minutes - hot again. Haven’t checked the coolant yet, but probably empty again. Can’t find a leak - could a blown head gasket burn off a radiator’s worth of coolant in half and hour with nothing out the tailpipe and no previous warning? I planned on driving it 140 miles tonight, but I’m thinking bad idea.
Yes, a blown headgasket can go through that much coolant (remember that the water jacket is under pressure at the same time that the cylinder is unver vacuum).
A compression leakdown test should answer the question definitively.
And yes, a 140 mile drive tonight is a bad idea.
Check the color of your oil. If it’s a light brown/tan you’ve got some water mixing with it. Also, does the exhaust look a little white? My son’s car was sucking in so much water it looked like a Stanley Steamer!