Would It be worth putting one that came off a 2.9L 4X4 onto my 4.0L? I found one on craigslist for a few hundred bucks. My mechanic says he wouldnt waste 1200$ on a new A4LD because my 4.0L engine could blow at any time, they suposedly have head problems and mine leaks a tiny bit of coolant into the #1 cylinder.