Hi everyone, happy Winterfests (of varying kinds)
My car has been making the same noise for the week-and-a-half I’ve owned it, but I’m now getting suspcious that it possibly should not be there.
The noise is a mechanical roughness that is not the engine or exhaust note itself, but seems to be something else. When you are moving along at a constant speed/revs, the engine is fine - as smooth as it could be, I think. But when you add throttle, the noise comes in, and the harder you press the throttle, the louder the noise gets.
To my mechanically inexperienced mind this suggests air intake issues. The noise behaves in the same pattern as an induction noise, as on the K&N induction filter I had on my old car, insofar as it directly responds to the amount of throttle being applied. But far from the K&Ns pleasant throatiness, this is a sort of mechanical, clattery sound (though it is fast, constant and not that loud). The car has the standard airbox/airflow meter, and has just had a complete inspection and service done by Dandycars (the MX-5 specialists) before they sold me the car. I will be taking it there tomorrow (if they’re open) to try to have this looked at under warranty, but I have a feeling that as the car was like this from sale they will claim that all 5s are like this or something similar.
I thought this was probably the case until I had somebody last night who has had 2 Mk1s (one of them until just a few weeks ago) try the car, and he confirmed that mine does sound a little rough. Its not a nice roughness, like the twin-cam roar that the car brings me at higher revs (love that!) - this just a laboured, mechanical sound.
It is not directly correalative to revs, but to throttle application, so I really cant think of anything but induction that could be causing it - but I may be wrong, what else could exhibit that sort of pattern? I’ve read about HLA noise, but I don’t know if this is the same pattern being exhibited. Also, HLA is supposed to quieten down whereas this does not fade after a long drive.
Worrying about this is somewhat hampering my enjoyment of a car that is otherwise an absolute joy (agile, playful and somehow getting around 37mpg!). Well, that and the awful radio reception which I’ll post about in the correct area.
So, er, please help - it’d be great to go into the specialist tomorrow with some prior knowledge!
Many thanks [:D][H]
I have no idea myself, but if you get no joy with Dandycars (who I have had problems with in the past) keep going round to the Blackwall Tunnel, through and down the A2 to Chatham. Mark at Freelance Mazda will tell you if anything is wrong. I wouldn’t trust a Mk1 or 2 with anyone else.
Only suggestion I can make is that it sounds a bit like pinking.
Except MX-5 engines can’t pink ;o)
WHAT [8-)] The guys got a mk1 surely if you advance the timing enough it will pink…No? I look forward to being proven wrong [;)]
Sorry - I was thinking of something entirely different, ie the old ‘it’s not got tappets, it’s got HLAs’ threads - shows how mechanically minded I am!
Well I don’t know - I haven’t advanced the timing, but I only got the car 2 weeks ago and I’m the eighth owner according to the V5, so its possible that an owner along the way advanced the timing.
On the other hand, the acceleration doesn’t seem greater than a 1.6 MK1 should have. I’m getting about 36-7 mpg on a combined cycle (long journeys), don’t know if that’s a clue.
Reading up on HLAs and tappets et al, this doesn’t seem to be what it is. And Dandycars would probably have spotted that before selling the car, espcially as they’ve given it a one-year warranty. Whatever it is, it doesnt seem to be adverseley affecting fuel consumption or performance - it is merely irritating.
My dad and I are going to have it up on jacks on Friday to check the exhaust/cat/manifold regions for any holes, worn gaskets, or leaks of any kind. It is good to know that if we spot anything the car is warrantied so will be fixed free of charge.
The noise is merely annoying, rather than actually obstructive - but I would like to at least know what it is, where it’s coming from etc.
Will post results on Friday evening/Sat morning. Any other suggestions between now and then would be MASSIVELY appreciated as my mechanical knowledge is poor, and my dad’s knowledge is 40 years old! If only I was bringing him a Spridget…
Happy not-quite-NYE everyone [Y]
Cheers
Has any one checked the alternator, or jockey pulleys, My step daughters Fiat started making noises from the front the engine,changed the alt belt and gave the alternator a squit of wd40m and round the jockey pulley no noise
alan
Not just jacks I hope, you MUST use ramps or axle stands HNY to you
It sounds like the heatshield on the exhaust, I can’t remember if it’s on the manifold or the first section - sorry to be vague but it sounds like a problem I had and I can’t remember excactly.
Cheers Geoff - this was made abundantly clear to me a couple of years ago when I had my old Fiat Seicento Abarth up on a jack, that promptly fell over and very nearly left me with a considerably more flat head. Rather - considerably more dead…
Big big zillion-tonne hyraulic lifter and axle stands all waiting in the workshop (my dad uses for kitcar and kitplane work). I’ll let you know what we find in our safety-conscious explorations [Y]
MX5 OC - your safety first…? Haha [:D] - my car doesn’t even have airbags or side impact bars [6] now THAT’S livin’ on the edge…
** disappears singing Aerosmith ** [8]
Ok, results are in.
We had her up on axle stands, and traced the noise to the front section of the exhaust. Specifically, the can in the front/mid section, after the gearbox, shortly before the gasket assembly that joins on to the rest of the pipe. The rattle seems to come from there. Also the join just further along seems less than perfect - when my dad covered it with his gloves the system was quieter, so I suspect these two factors are combining to cause the general noise
If they’re open I’ll be checking in at Dandycars tomorrow to make a claim on that warranty. At any rate, I’m glad its that causing it - a disposable part that is not very expensive - rather than anything more inherent and serious.
Judging by the size of the backbox and hearty note I also think the exhaust may be a mild performance mod one - not sure how to tell.
In general I’m thrilled - having the car up on stands allowed us to see the excellent condition of the underside. The rear section of the exhaust is clearly only a couple of years old, and everything else is rust-free - I imagine plenty of bits have been replaced in 19 years. Also, there seems to be lots of underseal which is reassuring - and explains how the car has survived in such good nick for this long.
Question 1: How can I tell when the undersealing needs redoing?
Question 2: Dad also explained that the variation in bodywork surface texture under the mid-line is due to rustproof paint - is this standard, or a sign of a very cautious owner and a respray at some point?
Either way, I feel so much better about the car having seen how good it looks underneath. I’m struggling to find anything more to be paranoid about now - clean underneath, clean under bonnet, clean bodywork - just an exhaust front section away from perfection. That is until I get bored and flush and consider SUBTLE mods (rigidity, brakes and possibly ride height are priorities I think - no extra horses needed).
Happy Friday everyone - especially the poor sods who’re already back at work! [B]
A bit random, but is the noise you a describing similar to if someone poured small stones down a metal pipe?
Got the car inspected last week, but have been away setting up the cars for the PistonHeads show hence no time to report back on here!
DandyCars took the car up on a ramp and we looked around. They told me it was a decat (should really have told me that before selling it to me…) and after coming out for a drive for me to show them the noise, they told me that its a resonance in the front/mid section of the pipe being caused by exhaust pressure in the less-than-brand-new section of the pipe. They said something like normally the cat sits there and [increases/decreases?] exhaust pressure.
As is probably clear by now, I got a bit confused, so in the end decided to leave it for now (I had places to be!) and perhaps get an inspection somewhere else. But I am concerned that any garage that inspects it will just find fault for the sake of it, in order to get me to pay to repair/replace things that actually aren’t broken.
Ultimately, the noise is no more than mildly irritating, and at least knowing that the car is decat explains why it is a little louder than some MK1s. Its nice to know, at least. I am less than impressed that I wasn’t informed of this before I paid for the car, though. I don’t think they deliberately kept the info from me, I think that it just hadn’t been relayed from their mechanics to the sales/management people.
For now I would just like some opinions on the ‘resonance’ theory they gave, if you please [:D] thanks in advance!
Basically i’d probably go with it.
A decat in effect makes the engine sound ‘raspier’ would be the only way to explain it. Sounds definitely plausible and it makes no odds really to the running of the car, i know what you mean on it gets annoying…but hey i went and plonked a turbocharger in and now i can’t hear the raspiness over the noise of a 2.5" catback exhaust system.
I’d suggest that as you’ve found it’s a combination of the decat pipe and a loose heatshield or two. Ultimately I think your being a little oversensitive about the fact you weren’t told as it is a really inconsequential component on any mk1. This is due to the fact that without it you can still pass the emissions test on the MOT and also it frees up a few horse power and also it makes sure your not going to go back complaining that the car doesn’t feel as fast as it should do, because the innards of the cat have broken up and are now suffocating the engine.
Please enjoy the car, and don’t worry about anything 
If you want to spend £140 quid on a new cat to get rid of the noise feel free…alternatively you can get a silenced de-cat pipe that will bring the noise level down.
I have a decat pipe on mine and it makes similar loud raspy noises, best described by someone here as “pebbles being poured down a drainpipe”. When in the car it sounds like it’s coming from the passenger footwell area.
Thanks for the replies guys - this is all very reassuring to hear. The car is an absolute treat in all other respects, this is just a niggle and if you all say it is ‘normal’ then I can and will stop worrying about it - and most of the time the stereo drowns it out anyway! Crucially, the payoff is that the exhaust note is really loud and monstrous at higher revs, which I love.
Particularly as for a week I’m currently in a company car ferrying to-and-from the show we’re doing at the NEC. It’s a 2-litre Mondeo Diesel. It is very quick, very quiet, comfortable and economic. I love the clever cruise control and being able to effortlessly overtake everything on the motorway, with minimal noise and minimal fuss. A fantastic cruiser. But once you’re off the motorway, everything just seems remote and awkward. Having spent most of my driving life in things small and sharp, the differences are telling.
So a slightly raspy MX5 that steers like my old go-kart (RIP) seems more and more like a godsend!!!
Next stop: induction-ville. Not forced induction mind - Im not after more power, just aural perfection!!! Pipercross or K&N I 'spose…
Thanks guys - hope you have a top weekend. Much of mine shall be spent on the fabulous M1… erk [:S]
I agree. Mine has a rattle from the heat shield that has been more noticable since I had the de-cat pipe fitted. I know it to be th heat shield as I have been under the cat and rattled it!
I see mx5parts sell a s/s mid pipe that doesn’t have the heat shield. Has anone fitted this? I wold be worried about heat in the the trans tunnel as a result…
I have no heat shields anywhere on the exhaust system, the one’s fitted to the underside of the floor are still there. I have no problems with a hot centre console even in the 33 deg sun out here. Fixing the cracked boots on the gearlever housing can make a big difference to the heat issue------------------