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I'm looking at a 98 Mazda 323 1.8L with a rebuilt engine. Basically, a mechanic bought it cheap due to shot rings and rebuilt the engine to sell it at a profit. He said it's the fifth engine he's rebuilt.

Is there anything I should look for to make sure he actually did the rebuild correctly? Any particular questions I should ask or tests I should do?

All Rebuilt Engines are NOT Created Equal!

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There are general things which you can do and look for to examine the mechanics work. These are not fool proof, but should give you an indication of the level of work the mechanic produced:

  • Does the exterior of the engine look clean? In order to do a good rebuild, you need to have a clean block and head. If they aren't clean, what do you think the inside of the engine would look like?
  • Does it appear to have new gaskets? If you look at the head gasket (should should be able to see it peaked out between the block and head), it should have a clean and fresh appearance. If you can see it and tell that it does not have that new look to it, the work was probably not done as suggested.
  • If you can do a compression check on the engine, you can tell if the engine is up to snuff and working properly. This is very non-subjective. Either the cylinder pressures will be at spec or they won't. If they aren't, the engine wasn't rebuilt correctly.
  • If there is an oil pressure gauge on the dash, ensure the pressure is good. Before an engine is broke-in completely, the oil pressure will be a bit higher than normal. If you see the gauge and the pressure is down towards the low end, again, the engine was probably not rebuilt correctly. It should have plenty of oil pressure.
  • What does the engine area look like? Is there a lot of things not reconnected or does there look like things are missing? If so, you can probably trust the level of effort put into the engine is not up to par.

These are just a few things, but hopefully it will give you an idea.

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  • Anything else you can think of would be appreciated... :-)
    – Robert S. Barnes
    Commented Jun 26, 2015 at 13:39
  • How clean are we talking about? Should it look new? Could you link to a good example image of how the engine should look if it's been properly cleaned?
    – Robert S. Barnes
    Commented Jun 26, 2015 at 14:09
  • Clean is just and indicator, not the end-all-do-all. I mean, someone could pull the engine, clean it up (on the exterior), paint it, throw it back in the engine bay and call it a day. It would be clean, but is not going to run any better. If I paint the items, I will paint them separately. Meaning, you'll will still see fresh metal on the mating surfaces (some of the surfaces can still be seen when assembled). It may or may not be painted. When I say clean, I mean clean. Like I said, if they cannot take the time to clean the outside, what does the inside of the build look like?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jun 26, 2015 at 14:20
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With a rebuilt engine it would cost you some money and/or time to open it back up again, and inspect the re-builder's work to see if it is well done or not. So, basically, you are going on trust: either you trust the mechanic to have used quality parts and done a good job of fitting them, or not.

Perhaps the best way to make sure would be to consult owners of his previous engine rebuilds. If they have had a good experience with his work, that will mean he can be trusted and you can go for it. A serious person will have no problems with putting you in touch with previous customers - he will know the feedback will be globally positive, and a good reputation is essential in this line of work.

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