1999 deville
 

my dad just bought a 99 deville that had sit for a few years we charged the battery and got the engine running sounded good.After we trailered it home and drove it it started heating up.Temp got up to 220 or so no smoke from tail pipe just steam passing radiator cap from overflow.Refilled the system let idle and no overheating but just as soon as you drive and get up to speed temp rises and starts bypassing rad cap.We have replaced the water pump radiator,checked purge line and still problems.I also removed all plugs and checked compression all cylinders checked 180 psi. The engine dosent skip and runs good other than this overheating and pushing coolant from the system. Any one have any suggestions?
Mark