Does it still run? i blew my head gasket once and had about 20 psi of compression in the front cylinder, but it wouldnt heat up, i drove it on three cyl. for about a week untill the head gasket came in. it blew in-between cylinders and it would leak compression from #1 into 2. so it might be blown. but i have no idea why it would just let go after just sitting..