Not a valve seal. More like "or something" as in head gasket or cracked head or block. Condensation indicates a coolant leak. Steam blowing out indicates it's under pressure so time for a teardown. If you have a leakdown tester you could try that first. Let the engine sit overnight then before starting it loosen the oil drain plug until oil drips out. If antifreeze or water comes out first, well................ Antifreeze in the oil will wipe out bearings in short order. Sometimes, what looks like steam is actually blowby from bad rings. And sometimes, condensation accumulates because of a bad PCV valve.