Nissan Xterra engine noise

I own a 2008 Nissan Xterra with 34,000 miles, purchased used from a Nissan dealer (near San Francisco) when the car had 20,000 miles. It had previously been a rental which the dealer had acquired at auction in Arizona. So far I have been happy with the car, but about 3 weeks ago I noticed a tapping sound which sounded like it was coming from under the hood. I first noticed this when I stopped at a stoplight coming back into San Francisco from Sacramento. The sound persisted, but I could only hear it if the car was warmed up and I had been driving it for at least 20-30 minutes. Also I could only hear it when it was in gear (reverse or drive) not in neutral or park. The performance of the car is otherwise fine and the noise in not noticeable when driving - only when stopped (it?s very subtle and not very loud). I took it to my mechanic (reliable, honest mechanic I have been using for years) and he heard the sound. He asked me to leave it with him and he would check it out. However, since it required driving around he was not able to easily reproduce the sound the next day. I then took it to the dealer. They could hear the sound and first changed the oil and oil filter. This didn?t make any difference in the noise. They then did a more thorough diagnostic and I think they mentioned something about low compression (although I?m not sure about this). They called Nissan and came back to me with an approval to put a new engine in the car. Since the warranty for the engine and transmission is for 60,000 miles this won?t cost me anything. The dealer has been very accommodating and I?m appreciative of all they?ve done. I went back to my mechanic and told him what had happened. He was surprised and said it hadn?t sounded like an engine noise to him. He thinks they might put a new engine in and the noise will still be there. In any case the engine is on the way and I am due to have it put in. Sounds like I?m coming out pretty good on this since I will have a new engine at no cost, but I?m curious about what?s causing this. I would like to get other opinions.



Any thoughts on what might be causing this noise? Any potential problems with swapping out an engine? The dealer told me they won?t know more until they get the old engine out. What d?ya think?



Thanks. Gregg Magrane

Let them change out the engine and see if it fine (99% likely).

A dealer and car maker usually has strong evidence/diagnosis before applying/paying out a warranty claim of this magnitude.

I had a 2005 which looks like yours. I bought it new and had a lot of problems with mine. At 30,000 they had to replace the timing chain and all the guides. My engine was very noisy, but it was making a whining noise. Sounds like there taking good care of you if there replacing your engine.