I own a 2004 Kia Carnival automatic, which is idling rough and blowing grey smoke at start-up. It also periodically doesn't have as much power on acceleration as it had. A bottle of Risolone did improve matters, but it's also burning oil. I've monitored the overflow on the radiator, I cannot detect that the water is decreasing. My mechanic believes the head gasket is going and has told me that these cars were renowned for this problem because of the poor engines. My mechanic has indicated that he could work on the head gasket, but I would be better with an engine replacement. Otherwise, the car is in good condition, and has only done 112,000 km. I have not yet approached Kia, but my mechanic has quoted around $6000, which is about what the car is insured for. However, I have a mechanic friend who works on cars, who has advised he and a mate are happy to do the work if I can find a secondhand replacement engine. I've found a secondhand 2006 manual Carnival with a 2.5-litre engine at the other end of the state. What I was wondering, was whether that model still had the issues of the 2004 engine? Also, would there be any problems putting an engine from a manual car into an automatic?
It is likely that there is a head gasket problem; it was a common issue with the early Carnival. Buying a secondhand engine is inviting trouble. It could also be struck down with the same problem and you could find yourself back in the same situation. I would be doing the head gasket rather than buying a secondhand engine, that way you know it is fixed.