Does this sound like the dreaded knock oh so many NCs fall too

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: MK3 NC
  2. I’m based near: Bristol
  3. I’m looking for technical help or recommendations on: An alarming engine rattle on startup

Hello,
For the past 3 months now i’ve been having a very concerning rattle on mostly cold startups (sometimes after heavy driving if i restart the engine after 5 minutes it does it but much quieter and shorter) but never during actual driving, i’ve covered about 3000 miles in that time and revved the absolute ■■■■■ off it (whilst warm) and it hasn’t change drastically, maybe a smidge worse.

I thought it could be a timing chain tensioner but my mechanic after listening to a video of it said he thought main bearings or rod bearings, but some people on the euro owners group say tensioners, some say rod bearings, some don’t hear anything wrong, i’m completly at a loss.

I went back to the dealer i bought it from (as in the UK you are legally entitled to a 6 month warranty) and they eventually acknowledged it but said they wouldn’t repair it as it wasn’t likely to fail soon, they said potentially timing chain tensioner. I called them out saying they have to repair it and they are ignoring all my emails and phone calls so whatever it turns out to be i’m going to have to take them to small claims court to pay for it.

This is my one and only car to get me to university and work, i really need to get some second opinions on what it could possibly be and if i’m best off just selling it to a big company with the problem and just letting them deal with it.

I have a few video clips below (or i don’t because of the limit to one item of embedded media).

I will be so incredible greatful for any of you wonderful peoples help/suggestions, it’s causing such a great deal of stress and anguish.
Thanks,
Zdos123

Edit : I’ve tried different oil filters, going from cheap chinese filter to mann helped but going to mazda made no difference. The noise also compleltly dissapears if i crank the engine before starting.

2

Here’s the other clip

3

I am by no means an expert on MX-5 sounds but, in my experience with older cars, big end or bearing noises are very evident when driving, particularly when accelerating. The videos are rather too short to be of much use.

I hope someone else can be of more help, as I understand and sympathise with your worries.

David

4

That does ease my worries somewhat as this noise is completly absent when driving, also as far as i know with rod knock it causes quite a vibration if i recall correctly?

5

Is this a 1.8 model. If so they can suffer from problems with the crankshaft ( they are none to brake). How often is the oil changed. or check’ed . Do you use a lot of oil

6

Try taking the serpentine belt off. I had a similar noise on my 07NC.
The idler on these are prone to failure and it does sound like an engine knock when they go.
Where abouts are you near Bristol?
I’m just up the M5 from Bristol NR Dursley and happy to have a look/ listen if you’re close

7

Doesn’t burn through any oil at all, i check it weekly. It is also a nc2 1.8.

8

I think it’s still the same pulley set up on the NC2 as the NC, I’m sure I’ll be corrected by someone if I’m wrong.
Try removing the belt and fire it up for a short bit. If the noise has gone then replace the idler and tensioner pulleys. It’s quite a simple task. I bought mine from Autolink

9

i’ll give that a go, it’s a bit problematic because it rattles so intermittently, it does it a lot when i don’t want it to but whenever i try to show it to someone it stops doing, but it might be good just to check all the pulleys and to refresh them anyway.

10

That sounds just like mine was, it rattled on start up, sometimes on idle but disappeared when going fast.
This was the tensioner I replaced on my NC, it solved the problem.

11

You would suffer from low oil pressure with badly worn big end bearings.