so this probably doesn't constitute as a tech tip, but i figure the info from my personal experiences should be of help.
the point of this thread is to give my opinion of what parts people should look for in a junk yard as opposed to the parts you are better off buying at a parts store.
the parts i would advise against going to the bone yard for includes:
any electrical components such as map sensors, oil pressure swithches, fuel pumps. the list goes on, and i think you get the point here. now one can always argue that you can test the item right there with a ohm-meter, but i prefer these parts to be replaced with brand-new components that have a better than 30 day warranty.
certain mechanical devices such as water pumps should be avoided from the bone yard. who knows how long the device has been sitting there, wasting away. and especially for the caddy engines, a water pump is something that should be replaced with a new component, not used. even an off-brand cheapie water pump is better than a salvaged pump.
tires. if you're really in a jam for cash, then a used tire from the junk yard may be needed. otherwise, a good used tire warehouse or a discount new tire place will be the better choice.
parts that i advise, yet are hit and miss:
fuel injectors, alternators, starters, ecm's, radiators, shocks, engines, transmissions, power steering pumps, rack-and-pinion steering gears, power accessory devices, drive axles, wheel hub bearings, air-ride suspension motors, distributors, yadda yadda yadda.
the reason i say hit and miss for the aforementioned items are for this reason:
you never really know how these items have been treated when last used on the car you are taking them from (in the case of a you-pull-it yard).
in the case of the alternator, starter, and the radiator, you can take them from the bone yard and have the devices tested at basically any auto parts store and for free too! the radiator though im not too sure about. if any of the devices are defective, the bone yard will usually take them back under warranty and exchange it for something else, or let you pull another peice of if that is what you want. as far a testing the radiator, you can just take it home and run water through it via a hose and see if there are any leaks that surface. make sure there is decent pressure from the hose so that the water pressure will hopefully find a leak before you go any further and waste your time.
the ecm and the injectors are more of a trial and error thing, as there is no way to really test them other than to try them. you can always check the injectors with the ohm-meter, but that will not be able to detect a severly clogged injector. as far as the ecm goes, i know of no way other than to install it and see how it works out.
steering gears, steering pumps and the like can usually be visually inspected. if you see any fluids in an area that should not be leaking (hence the entire device), than you're wasting youe money. find another one. with a steering pump, try to spin the pully, if it is loose or makes any small ckicking sounds, than i would look elsewhere. if the steering gear appears loose, if the boots on the device seems worn out, or it is leaking, then you get the point.
drive axles and wheel hub bearings: again, a good visual inspection will be needed before you waste time on a defective part. in the case of the drive axle, i usually replace the boots on them and put new grease in them. make sure there are no apparent bends/twists/burrs or any thing of the like when inspecting such things. wheel hub bearings are quite simple: if you cannot freely turn the part you have purchased, or if it is too loose and rattles, then it is bad. in all honesty, i would just consider getting a new one, but you can find decent hub bearings in a bone yardif you inspect them well enough.
shocks and struts are also something to inspect very carefully. i would not recomend purchasing a pair of rusted shocks/struts.
air-ride suspension motors, power accessory motors: from my experience, these are true hit and miss items. you can test these items (look at your shop manual to see how) before you install or buy them. if they are defective, again, exercise that warranty that the junk yard offers.
transmissions and distributors: a tranny is something that is a true hit and miss item as well. either they work, or they don't. you can always spend the extra cash by having a bench test done (i think this applies to trannys, never had one tested myself), and in that case, be sure the tester is reputable and well qualified. still, if you purchased a bad tranny, you're out the money it cost to do the test. a distributor is rather easy: if it is cracked and bent. it is no good. when using a salvbaged distributor, i would recomend buy the pick-up coil, hall-effect switch or whatever so you don't have to deal with a possible defective part. i also HIGHY reccomend buying a new dist. gear.
engines: not a hit and miss item if you rebuilt it. the warranty will usually expire the moment you take the engine apart, but this way, you will have the knowledge of what is needed to get the engine back in running order. now you coulda always just drop the engine in your car as a plug-and-play, but when you start to hear weird noises, don't complain. the warranty will still be valid (in most cases) and you could exchange it...ideally. my advice however: REBUILD IT!!!
BTW, make sure the engine has no HOLES in it before you buy it or pull it!
that covers the big stuff...i think.
things to consider when buying from a junk yard:
price shop, a good bargain in this case is hard to pass up.
get warranty information, some salvage yards like to throw the "you're not a professional and you installed it so you're screwed" phrase. get information BEFORE you spend time on a project like this.
a you-pull-it yard is MUCH cheaper and i highly recomend this type. if you're pressed for time, the price shopping will come in handy and things will still be reasonable.
inspect, inspect, inspect!!! look the part over and over again. even in a pre-pull parts warehouse, inspect the items you wish to purchase with a mission up your ass! don't get cheesed by not doing so.
that should cover the basics of bone yard shopping.
if there is anything anyone would like to add, pleas do so. the more information on personal junk yard experience is a must for everyone who takes this rout in auto part shopping. have fun, illumina