If it is anything like an old Nissan I had I would bet blown head gasket between the cylinders, when it runs do you get steam out the exhaust or water in the oil??

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2001 Ranger Edge 4x4 , Stepside,FRF decals, 4.0L SOHC decals, Primus IQ brake controller, curt 2" rec. hitch, custom winch mount,
Tinted glass, Yellow BUGGMAN OVALS a real treat to have. OHC, CB, night vision goggles, 36" periscope,
DiabloAmarillo = The Yellow Devil