2010 NC Tapping/rattle from engine

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: NC (2010 20th Anniversary)
  2. I’m based near: Newport, South Wales
  3. I’m looking for technical help or recommendations on: Tapping/rattle sound from the engine.

Hoping someone can help. Acquired my NC a year ago where the previous owner had what she called a ‘metallic tapping’ noise coming from under the bonnet when revs were at around 2000-3000 rpm.

The sound pretty much only appears when you’re gently touching, or lifting off the accelerator. So, if you’re on a flat motorway and maintaining 60-65mph, the rattling is pretty much constant. It doesn’t get louder or faster at higher revs, so doesn’t appear to be rod knock. It also occasionally makes the noise briefly when the car starts.

I replaced and flushed the engine oil a couple of months ago and am convinced that it made a the sound go away a little, but in the last few months it’s pretty much as loud as it was when I first got the car.

My local garage told me that it was a benign sound coming from the engine and to fix it would probably require a costly engine strip/replacement. Given it doesn’t appear to be a fatal issue I can live with it by turning the radio up, but wondered if anyone had had the same issue before, and if it was a simpler fix?

2

I would read this below and similar stories and have a look first at the pulley(s) of the auxiliary belt

3

My metallic rattle disappeared when I slipped the serpentine belt off. Idler and tensioner pulleys were on the way out at 90,000 miles. Relatively cheap fix and it was my first job as a process of elimination.