1996 extended cab F150, 302 engine. 164,000 miles on clock. Was having persistent coolant leaks, replaced bad radiator and heater core. Coolant loss persisted, mechanic discovered a slow leak in the timing chain cover gasket. Mechanic recommended against repair because he also discovered that engine oil (not transmission fluid) is contaminating the coolant. I flushed the cooling system and in almost no time the new coolant was recontaminated. Other than for the timing chain gasket leak, no other external leaks of coolant, or of engine oil have been detected. Can anyone suggest a likely way that engine oil is getting into the coolant?

 

Head gasket, cracked head, cracked block. Possibilities.

 

Dang it! Almost wish I hadn't asked. I think mechanic was right. Drive it till it dies a natural death.