I recently purchased a 1980 Chevy Impala with 74,000 miles. On the third day my engine ground to a halt. My mechanic replaced it with a used one that lasted about five days before it started making grinding noises, and produced metal shavings in the oil.
He is now about to install a third engine so I asked him to check it out thoroughly. He said a test drive after it's installed was all that he could do. What could cause the two engines to turn to junk? My back yard mechanic friend suggested replacing the water pump, oil pump, and timing chain on the next one. Would this help?
Used engines can be risky business -- most of the time you're guessing on internal condition, maintenance history, or even the legitimate mileage. The best way to judge a used engine is to run it while it's still in the original vehicle, but most junk yards have them previously pulled and sitting on a shelf.
If that's the case, let's be sure the engine turns freely, and then do a careful inspection of the oil. You'll be looking for any signs of metal particles, excessive sludge, or antifreeze contamination. Inspection of the spark plugs is also helpful in determining oil and coolant consumption. If the engine still looks good at this point, then cross your fingers, and install.
Once the engine is running and reaches operating temperature, listen carefully for any significant engine noises. Then look for notable fluid leaks, and/or smoke or vapor coming out the tail pipe. The loss of the first two engines was probably just your luck of the draw, and I wouldn't suggest doing any significant work to the next one until it's been on the road and proven itself.