The sounds seems to occur from 2000 to 3000 rpm range, and they are very distinct "clicks". Could it be indication that the timing chain and tensioner needs to be changed? For background; a couple months ago the mechanic said they found pieces of the timing chain tensioner in the oil pan but they were unable to determine if it were pieces from a prior change. For what its worth carfax found no such service ($40 down the drain ) Also, I have codes for p0011, p0021, and p0340, and I heard the first two relate to timing chain tensioner. I have a recording of the sound and can provide more occurrences of said sound.

BTW car has 268k miles .

Definitely sounds like something clashing around in there. What year is your M ?

It's the 06 model, I think this means it has the "nonrevup" vq35de. I'm planning on putting seafoam if the noise go away. Motor is nearly 270k miles so who knows how much carbon has built up.

Open the 710 (oil fill) cap and look.

I would source a replacement motor, I don't really see the point in tearing apart an engine with that kind of mileage just to fix a timing chain tensioner guide.

What would be the labor cost in just replacing the tensioners? I know replacing the whole chain /tensioners set would be over $1000 Also, what is your estimate labor cost be in replacing the engine?

12-15 hours or so. If you're going to have to pay a shop to do the work I suggest you sell the vehicle while it's still running and buy something else. You're still going to have a high mile chassis even with a low mile engine.

Yeah we decided it's not worth it in the end. I actually used seafoam today and added more oil (oil level was between "high" and "low") and the sound barely comes back and the engine seems stronger too. Just going to run till the motor gives out.

Regarding getting a new car, I was eyeing in getting another used m series car again for $10k but can't decide between early m37 models or any of the m35. What would you recommend?

$10k gets you a lot of car, you can get into a fully loaded excellent condition 2009-2010 M35 with the VQ35HR motor.

Unless you want to step into a G, you can get a G37 for about that price.