Nissan 3 litre diesel

I've heard a few horror stories about these motors. What's actually the problem with them? TIA.

Yes the worries you hear are true they are not wives tales. As far as I am aware the problem Is over boosting of the turbo. This causes melting pistons and other issues. The fix is a complete engine rebuild and a kit called a anti detonation kit installed too. Don't touch that engine in early forms it is a nightmare

over boosting doesn't cause it. thats a symptom of other issues.

there has been no official cause to the ZD30 blowing pistons. note- thats not the common rail version of the ZD30. common rail one is fine, just the earlier vp44 pump version that has the issues.

there seams to be two main things.
early on it was either a piston, some say rings, issue. basically weak. later ones didn't suffer quite the same failures as the early ones did.

however there is still a few issues.
one is the variable turbo is controlled by the MAF, unlike most other engines which uses the MAP. MAF gets dirty, reads incorrectly and operates turbo incorrectly and causes it to overboost.
however as the MAF also controls the fuel, the fuel goes a bit wonky to.

then there is the injection pump which often wears the timing valve and timing runs retarded.

intercooler known to crack and you have less air flow than what the MAF says it has.

all these things equals higher temps and the pistons fail. the difference compared to the early ones is the heads are normally cracked as well from the excessive temps.

BUT, the navara version of the ZD30 doesn't have a MAF and the amount of failures is a lot less. its also lower powered.

there is also a non-turbo version which i don't know much on.