Hello, I am about (I think) to purchase a 1990 740, it has a turbo but their is one problem, it has an engine knock. The knock occurs when the engine is under load(with one foot on the brake, in reverse, drive and in neutral when I rev it quickly from low to high rpms). It seem that the knock is occuring above the head gasket(I checked with a stethoscope and I'm 60% sure) The engine also idles roughly. The knock seems to be on the upper half of the engine. My question is, would an engine idle roughly becasue is has thrown a connecting rod bearing or other major bearing (which could produce a knock). According to the orginal owner, this car run perfectly until one day when he past someone on the highway, when all of a sudden the engine started knocking. I woulld think that the engine would still runs smoothly if it had thrown a bearing, but I do not no If I am correct in this assumption(perhaps the situation is complicated by the knock sensor).

I would love to believe that this problem is in the upper part of the engine(head), but I'm just not sure. Is it possible for something in the head to break off (like a valve) and produce such a consistant knock?

If anyone has similar expereince with this type of thing, advice would be greatly appreciated, I am but somewhat mechnically inclined. The engine is a B230FT...

Thanks,

Jim