Mk3/nc Engine Rattle Help/advise

Technical Area Engine, Transmission, Exhaust etc
2

Hi, new poster here but lurking around for a while, these forums where extremely helpful when I swapped out my standard speakers and wiring up the radio / amp, hopefully you guys and gals might be able to help with my current issue.

I have a 56 plate MK3 1.8L with 92,000 miles on the clock and absolutely loving the car. however about a week ago it started making a small rattle/clicking/knocking noise from the engine area. there is a video below which I took just as the sun was setting that will demonstrate the sound below - however the noise happens mostly while there is less strain on the engine and is obvious at around from 2,000 RPM on wards. Under acceleration or deceleration the noise seems to go - happens while it is out of gear and while revving can hear it slightly but as soon as you come of the throttle you can hear it clearly and then dissipates when going back to idle, this is the rule of thumb as in first gear when you get higher revs its clearer but later gears its not so loud.

As the noise wasn’t always there I continued to drive it to work and back for 2 days, approx a total of 50 miles, nothing really changed during this time. I was then able to take it to my garage, from the noise and characteristics they thought it was the timing chain, they noted that the engine was low on oil too - though I had no warning light and the oil pressure gauge looked ok - I do occasionally check the oil level, probably (obviously at this point) not as often as I needed to - but Im not an mechanic and the dip stick looked ok last time I checked was between the min/max (nearer the max) but admittedly was a fair few months ago.

Anyhow I needed a service and the back brakes done so got it all done at the same time.

Timing chain (kit) still has not fixed the issue though. thus why I am here and the research I have/am doing, so youtube is an amazing tool, I have learned a fair amount from some basic videos on how to start diagnosing noises and locations etc. 

So with that all said I have now had it back for a day and trying to work out whats going on, I had previously put an obd reader in and there is no errors or misfires (from what it can read) and I will be contacting the garage I took it to to try and find out more info, when I was talking with the mechanic he believes it might be a lower engine noise, however he has not said if he had found anything in the oil but then again I didn’t ask, As soon as I can find out any more info I will post an update here.

Here is a video of the noise while at Idle and moving around the engine

 https://youtu.be/lWKcW8GA8Ms


And this one is more static but can hear the issue clearer

https://youtu.be/RtT-OkehcCY

I plan on taking a third video with some help in the daylight and at different engine locations and RPM’s tomorrow as to get a clearer picture of where the noise is coming from.

So I would appreciate any guidance on what might be causing the issue and the next steps to try to diagnose/resolve the issue

regards

1 Like
3

Sounds perfectly normal to me, they are an agricultural sounding engine, it will never purr like a kitten.
Do an oil and filter change if it’s bothering you.

4

Thanks for the feedback, so I have had this care a year an a half, this noise wasn’t there until recently, also the full service included replacement oil filter, air filter and spark plugs - though looking at the invoice I just noticed he hasn’t charged me for oil which he has in the past, I trust this guy and have used him for a long time (had all my car work and a lot of my families car work done there too) so he may of not added it to the invoice to keep the cost down - but will get clarification on that.
Its hard to hear and thus the reason for the second video, the first you cant really hear it, you may be able to hear it around time index of 0:45 - 0:52
But its much clearer in the second video - time index of 0:13 - 0:17, 0:21 - 0:25 and finally at 0:36 - 0:39, the mechanics first impressions where “it doesn’t sound healthy” and that its a recent noise and I can hear it from the cabin doesn’t fill me with all that much faith anymore that it is “normal” but I know exactly what you mean as I have watched some videos with different cars and I am thinking to myself that it sounds normal… whats wrong with it.

Saying that, if it isn’t anything to be concerned about I would be hugely relieved, I love the car and have already started looking at other mx-5’s / considering engine swap and a load of other “too expensive” options

The only reason I continued to drive it for those 2 days was because it didn’t sound all that bad but its now making me nervous as I can constantly hear it when I expect it to make the noise.

5

I put this up quite a while ago, have a read.

https://www.mx5oc.co.uk/forum/yaf_postst103847_NC-serpentine-belt–idler-and-tension-pulleys.aspx

I’m not saying it’s the answer but you never know. Whatever happens it’s essential you check and maintain the oil levels at, or slightly above, the maximum mark on the dipstick.

Barrie

6

Difficult to tell. The first video sounds normal. This is a 2.0 with main bearing failure. You hear a sort of chugging sound on idle then a knocking when revved.     https://www.youtube.com/watch?v=4PFa91inYiM  

7

Yes i can hear the noise in the second video. Sounds like the old MK1 tappets but obviously this is a MK3. 

Personally I would stick some forte advanced motor flush in it, run it for a while to allow it to work and then do a decent oil change and see what happens. 

Some people get worried about using engine flush, but I have used it on some seriously high milers etc and never had a problem and fixed a few noises along the way

1 Like
8

im with bettabuilda on this one ,
remove serpentine belt , restart the engine and see if noise disappeares if so , change belt + pullys

9

Check the oil at least weekly or you are asking for trouble, a few months isn’t good enough between checks, especially on a higher mileage engine.

That lecture over in the camp of auxiliary belt and tensioners need eliminating from being the possible problem.

10

Yep, supporting the boys on this one.

The serpentine belt and more to the point pulleys have caused lots of confusion. When worn these do great impressions of a more serious fault(s).

Unfortunately it would seem that owners may have been persuaded to change an engine when the real cause is £75 of pulleys and belt that needed replacing after 50k+ miles in any event.  

It is easily possible to check the pulleys for wear as a worn pulley will have a lot of slack when manipulated with the belt pressure off.

It’s a lovely day, check it out.     

11

Belt tensioner on the serpetine belt ?

 

Common fault apprently.

12

Mine sounds like yours only noticed over the weekend when doing my thermostat and been quite close to the engine how noisy and industrial it sound

 

Sorry didn’t watch the second video…mines doesn’t sound like that under load,just a bit rattley under tick over*

13

 .  update ???

1 Like
14

Yes, what’s happening?

Barrie

15

Still working on it, took it to my brothers landlord who has had experience in the past with engines, he said he thought it was the hydraulic tappets, but had no tools to give a better diagnosis (just a listen) I work in retail so Sunday was my only day off thus far even though it is Easter, I know a mate who works at another garage and looking to get it over there soon, and the landlord has recommended a local garage that I am looking to take it to soon.

I have considered getting a few tools to start doing futher diagnostics myself but then for the price of the cheap ones I probably can get a diagnostic done for free/same as tool cost.

I’m a computer technician so I don’t know how useful any tools would be to myself in the future.

 

The one thing I have done though is notched the back side of the dipstick so to easier read it an checked the levels and they are at the second line on the stick, as my garage said it was low I presume this is now the correct level and he had replaced and filled the oil. - as others have said the stock dipstick isnt the easiest to read.

16

dont let them write off the engine until you have checked the serpentine belt + pullys

17

Update time.

I got in contact with the mechanic who done the service, they took the top of the engine off and looked ok (thought it might be a tappet issue until he found it have them - but while doing the timing chain probably didnt add much time to the work) as said before he thought it was lower end. It was the mechanics son that done most the work and will be getting back to me some point soon with the oil level and also if they found anything in it.

Took it to another garage today and they also believe its an “internal engine noise” but they don’t specialist in engine re-builds and pointed me elsewhere

After watching a video on youtube just as this all started there was an interesting video where they go through many different ways to try and diagnose the issue, one was ignition test, as this doesnt require tools to do - knowing the risk that prolonged run will cause more problems and even short runs may make it worse, I took the decision to pull spark lead out one at a time. - result the noise mostly went with the first (or last - the one nearest the front of the car) lead out.

 

I have now done aprox 150 miles since this has started and no change in the noise at the moment.

 

This somewhat tells me that the opinions at garages are correct and its not going to be an external bearing and furthermore a bottom end problem, is this a correct assumption?

Is it still worth while pulling the serpentine belt off?

Also a suggestion elsewhere on the internet was to use engine flush, while some people say its a bad idea as it may cause other issues, some say it may just be buildup, with what is known so far is this worth an attempt or not?

I am somewhat tempted to get a breaker bar as this may be useful in the future anyway will give me that peace of mind - unless the update, as I may suspect, may indicate it is an engine issue.

18

Taking the belt off ought to be part of the diagnosis.

It costs nothing other than time and maybe a few rapped knuckles.

19

Noticed your on the Miata forum discussing this, have you noticed on that forum every one is get stuck in worst case scenario and on this site every thing is approached with a much more rational approach and discount simple things first.

On the Miata forum I posted about my broken thermostat bolt and some one said use this opportunity to swap the engine out for a 2.5 engine …but all help is welcome.

 

 

 

20

Yeh, there is a difference, though I think I may just do that engine swap depending it is a rod issue and the cost of a rebuild - most comments I have read said the swap is cheaper? any experience there?