The only thing I can think of is for you to listen to the sound when you drive it. The wheel bearing usually is more of a whine type of sound and it is usually constant, although I have had them sometimes only whine when you go around a corner and put a load on one edge or the other. The half shaft's tend to be more a clunk sound and they usually start out making a noise when you go around a corner, but as they progress they become more frequent and regular, but they still have more of a clunk sound to them.
I know whine and clunk aren't very good descriptor's, but hey it's the best I can think of.
SVOboy: What you should do, on your 'vote' is just look at this as an opportunity cost. The question is what else could or would you be doing, if you weren't working on this car, and how much would it be worth to you in $. If you have something you else you could do which would be a better opportunity, then you should do that, otherwise, you can do this. (I don't think I explained that very well, but hopefully you get the idea.)
I asked him the color and he told me he could never see it but that's what they failed him for. We discussed and and the way I understand it is that if it's engine related (ie rings) then that is outside of the scope of this deal. I ought to be check it out tomorrow to see what's up. I don't have a compression tester handy but I will just pop off the exhaust manifold and see if I discover anything there.
SVOboy: I'm a little confused. Is the car he want's to have you work on already passed smog, or did it fail smog. On the smoking, several years ago I had a Dodge Caravan with a 3.0 Liter engine. One of the problems with that motor was that the valve guides were just pressed into the head's, with no lip or anything to hold them in, besides the press. If they were overheated, at all, they had a tendency for the valve guide to slide further into the head, causing the valve guide seal to have nothing to seal to. My engine had that issue, on one cylinder, so it smoked, decidedly, when you would accelerate and it smoked in general. At the time, it still would pass smog because the smoke from the oil didn't cause NOX or whatever other gasses they were testing for. It was embarassing to drive, but it was smog legal. I'm just wondering if something like that might be what your working against.
What I'd do is pull the plugs and see what they look like. Black and sooty, it's probably getting oil from somewhere, on that cylinder.
I think the most important thing is to get it in writing. List out what is expected of you, how you tell if it's done, and a cap on each thing as far as your expenses even if it's not done. You don't want disagreements after you've spent a couple weeks on this thing, so just lay it out beforehand.
Also, the A/C can be a big risk. You can't do much more than adding some refrigerant and tightening a connection. It'll probably fix it, but any more than that and you need some expensive equipment to recharge it, or a serious shop bill. So be careful to cap that at a resonable amount.
Indeed, he was very much in favor of a contract also detailing all possible outcomes.
Anyway, I'll see the junk tomorrow. I might suggest to him that he covers expenses while trying to sell the sentra and if he sells the sentra himself he can just pay me something agreed upon for labor or we could do such a thing but with the option of me paying expenses upon completion in exchange for the sentra, something like that. A/C is a pain in the *** but I'm fairly sure I can pop by the shop and use the snap-on cart for evacuation since it doesn't cost them anything,