On a straight four diesel engine Can you replace some pistons bearings and leave other unchanged , Will that have any negative effects on the performance of the engine

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    Welcome to Motor Vehicle Maintenance & Repair! Jul 2 '20 at 1:17
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    May not affect performance, but the ones that were not replaced will fail soon so you will do all that work again... May be a good plan if labor is cheap and parts expensive, but not a route I would take.
    – Solar Mike
    Jul 2 '20 at 5:53
  • @SolarMike Perfect advice. Jul 2 '20 at 10:21

NOTE: You state "piston bearings" ... which don't exist. I'm assuming you actually mean either the rod or main bearings which the crankshaft rides on, so that's what I'm going with.

Technically I suppose you could ... but why? It doesn't make sense for many reasons:

  1. When you get new bearings, they come as a set for all of the journals. You've got new bearings, why wouldn't you use them?
  2. When you don't replace all of the bearings, they'll (obviously) be different. The engine won't necessarily like that and could cause more issues down the road.
  3. If you have to have machine work on a single journal, it will be undersize. If you only did this to one journal, you'll have a journal which will have less friction on the single journal, which means the engine will be out of balance in power production.
  4. If you need machine work, a shop won't do "just one journal". They'll want to do all of the journals because they know you'll want to do them all.
  5. If you have to open up your engine to replace "just one journal" worth of bearings, why not just replace them all while you're in there. It's a lot of work to rebuild an engine. It only makes sense to be "one and done", meaning, do it once and you won't be redoing it anytime soon. More than likely if you don't do them all, you'll just be turning around and having to do the other bearings in the not too distant future.

I'm sure there are other reasons I could come up with, but hopefully this is more than enough to convince you.


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