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I confirmed that my piston rings were leaking after moisture got in and corroded them when I had the heads off. It's a 2007 Toyota Tacoma V6 4L. I took the diff and oil pan off, sent air through spark plug holes and confirmed it was coming from the bottom of the cylinder.

So I am taking each piston out and replacing rings. What is a routine checklist (measurements) and maybe machining (coating?) of each piston that I should perform? Or can I expect that standard rings should fit (one size fits all)?

RELATED: Likelihood of every piston ring corroding the same rate

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You cannot "assume" you can use standard rings. If you want to do it right, you need to measure the cylinder bore to see if you can use them or if you should bore the cylinder. There is a tolerance with every engine set by the manufacturer as to what is "out of tolerance". You can usually find these specs in a Haynes manual or the like. You also need to measure your cylinder for taper (top to bottom) as well as for out of round. Each of these will have a tolerance as well. You also need to check the piston itself for wear. You may have rust scoring on the cylinders, which would need to be taken care of (usually by boring the cylinders). If you have to bore the cylinders, you'll need new pistons as well. Pistons have a measurement check on them. You'd need to use a micrometer, usually at the top of the skirt. The portion of the skirt which is on the thrust side of the piston usually gets the most wear. Again, these specifications can be found either online or in a rebuild manual like Haynes puts out.

All that said, you may be able to get by with a re-ring and honing the cylinder walls. This would be the bare minimum you'd need to do to replace the rings. In order to do this, you have to tear the engine apart. It only makes sense to put new bearings in while you're at it.

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  • for honing, should I use a tool that looks like this or like this?
    – amphibient
    Commented Aug 6, 2022 at 14:29
  • @amphibient - Either will work. The ball hone (dingleberry hone) will do the better job, though. Trade off is, they are a lot more expensive. Either way, the key to getting the hone done is to ensure movement of the hone up and down in the bore (don't dwell). This creates the cross-hatch in the cylinder. Why do you want to hone in the first place? If you replace the rings and don't, the rings won't seat and you'll have blowby and loss of compression. Don't over do the honing, either. Keep passes equal between bores (IE: 10 passes each cyl). Commented Aug 6, 2022 at 16:00
  • youtu.be/f7JuMGsyDAg - This video talks about the regular hone, but the process is pretty much the same. Commented Aug 6, 2022 at 16:05
  • you think it's OK to keep the crankshaft in while honing? because i don't need to take it out to remove the pistons
    – amphibient
    Commented Aug 6, 2022 at 19:50
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    Yes. Both leave grit behind. It's how it does it's thing. The grit grinds on the smooth surface of the cylinder to get the surface finish you need so the new rings will seat. This action leaves grit behind. Commented Aug 7, 2022 at 11:48

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