most junkyard engines do have problems.....customers will bring them back just as fast, "theres a leak, or its making this funny noise...its amazing how someone who is so friggin cheap they wont buy a new engine, then they nitpick every little thing with a used one cause they think it should be just like a new one, well its not., i dont know about your junkyards, but ours dont have these"wonderful junkyard engines that have far less problems than a new one"......you dont know how the previous owner took care of it, were the oil changes done regularly? were they thinking they were mario andretti? did they flush the cooling system regularly? these are all unknowns....the junkyard will tell you what you want to hear so they can sell the engine, most only give a 7 day warranty on a used engine.....they know why! if you are very lucky, you can find one that will give a 30 day warranty, but those are rare now days.also, many people forget that the costs of repairs also include diagnostic time! alternator goes bad....why did it go bad? you need to check the system out....check connections, measure voltage drops, etc....then change the alternator....dont forget that is part of the cost, most people and places simply toss on another alternator and if it doesnt work, or if it quits after a few days, they assume its a defective part, because they have not checked the system out, to find the cause of the failure. thats what a Professional shop will do! and i emphasize PROFESSIONAL! not every shop is a professional shop.