I have an 01 Grand Cherokee in my shop, with no compression in #1, traced to a burned intake valve or it dropped seat, took the intake off and yep, valve seat done. I've read ton's of horror story's of sludge and the odd cracked head but nothing about valve seats. I have no history on it and it doesn't appear to have been overheated, full of coolant, no blown head gaskets and doesn't have the typical smell of an overheated engine. Thanks.