It seems plausible that the cost of rebuilding the engine would qualify as an "other loss," but note that the full phrase is "other loss caused by the breach." Rebuilding the engine isn't anything that he was caused to do by the breach. It was something he was required to do by the contract.

Why do we not add in the cost of rebuilding the engine as one of the elements of his damages (i.e., one of the things he is entitled to recover for)? Because we're going to give him the $8,000 contract price. That is what compensates him for the cost of rebuilding the engine. That's all he would have received if the contract had been performed, and the goal of contract damages is to put the non-breaching party in the same position that performance would have. We don't want to make him better off.

Now that you know all of this good stuff,