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Hi All - here's a curly one.. I've owned this '90 NA for about 8 months (do about 700 klm a week) and a few times, I've heard a high pitched squeeling noise under the bonnet, and it goes away before I can suss it out. It's NOT the fanbelt, and the other day (for the first time)it squeeled when I only turned the key to power, but not all the way to the 'hit the starter' position, so the engine wasn't running.. I'm now thinking it sounds like a dodgy relay squeeling (I did some auto electrics 30 years ago) and wondered if anyone else had experienced this, and maybe what is might be? And before anyone suggests - It's not Tinitus either - I know what that sounds like too ! .. hmmm...come to think of it - I haven't noticed the neighbours cat around lately, either... anyhoo- any help really appreciated.. cheers people Drek

Timing belt idler pulley?

If it sounds and acts like an accessory belt, but it isn't, timing belt idler is the usual culprit.

It's tinitus AND fanbelts.

I have heard of squealing relays before. Thought it was just another British car thing. The MAIN or FUEL INJ relay is switched on with the ignition to feed the ECU, coils and injectors. It's big enough to make a fair noise. Location is the front left corner of the main fuse block in the engine bay just in front of the driver. The MAIN relay does fail from time to time. Symptons may include weak spark (and hence power), sudden complete cut outs and occasionally the engine running almost impossibly lean when there's not quite enough power to run the injectors properly. If you did electrics years ago then you may be interested to know that you can prise the top cover off the relay and clean and adjust the points.

I was going to say dry alternator or idler pulley bearing, but its making the noise without the engine running. maybe a relay as suggested.

MazDaz66 wrote:I was going to say dry alternator or idler pulley bearing, but its making the noise without the engine running. maybe a relay as suggested.

Ahh yes - I didn't read the post closely enough! Sounds electrical to me...

One other thing that's switched on with the ignition is the fuel pump. I wonder if the noise is from fuel whistling through the fuel pressure regulator at the back of the fuel rail?

Squealing aircon radiator fan?

WOW - Thanks Guys - I gotta say it's great to be on the forum with you all - thanks for ALL your ideas, and I think the beer might just go to manga-blue - when you mentioned the fuel pump and the fuel whistling - it sounds exactly like that - The other day when I heard it - I thought it sounded a bit like a whistling kettle cutting in and out and having a bit of a spit, and it does it sometimes while driving- but I couldn't imagine anything under there that could make that noise.. - I'll either replace it, or turn up the stereo.. Thanks again everybody for taking the time to give your ideas.. Cheers Drek

No worries, Drek, welcome to the forum. After I posted that I thought what a dumb idea it was. JBT's comment about the fan was so obviously the source.

In any case a whistling MX5 is not a bad thing. At one stage I set my car up with a ridiculous amount of front toe out. Tyre wear was horrendous but I found that I could just run the driver's side wheel up onto the tramtrack and off again to make a fairly good wolf whistle. Made the trip down Brunswick St a lot of fun. Maybe you could eventually tune yours ....

Cheers mate - I did look at the fans when it first happened (I also wondered about the alternator bearings or the starter coming on without the solenoid kicking in), but the noise is too high of a pitch, and it spits a bit, like the motor is letting off steam (I don't rev it THAT hard.. and it did sound closer to the firewall - I might try waving a candle around under the bonnet to check for fuel leaks... or I might cut a hole in the bonnet, so when it happens again, I can poke it with a stick and see if the noise goes away.. I had faith that if it was something serious, it would expose itself (to the RACQ guy, anyway) at some point.. and my tinitus only sounds like the muffler baffles falling out, so I knew it wasn't that (or maybe the muffler baffles really ARE falling out?), and I saw the neighbours cat yesterday, so that ruled that out.. And hey - you know that wolf whistle trick belongs on youtube ?! When I was younger I had a wolf whistle mounted on the inlet manifold of my Chevy, but I never got around to using it, because the girls in my town just weren't worth whistling at... (jokes) Thanks again Drek

Drek wrote:I had faith that if it was something serious, it would expose itself (to the RACQ guy, anyway)

Can't always trust the RACV/Q guys.

A friend called them when his WRX started overheating, the RACV guy simply told him "the radiator is broken, you'll need a mechanic to fix that" and left.

Pam and myself arrived to help dodgy the car to state where it could be limped to a mechanic.

We removed the 6inch wide plastic CLIP ON air diverter that was covering part of the radiator hose.
And we simply saw it was just a split hose.




So yeah, the RACV guys can sometimes be lazy..... it was easier to say "radiator broken, they're about $500" than to spend 5mins looking and say "It's a blown hose, $10 to fix"

Don't laugh but a couple of weeks ago my rally car project (Escort) developed a high pitched squeal that sounded like a belt. I took the fan belt off, noise was still there..... Traced it to a tiny leak in the sump gasket!!! It was a high pressure whistle !!! Sounded exactly like a belt though

oh no - I don't even want to think about it being that - I know it can't be that because it farted before I even hit the starter the other morning... it sorta sounds like a high pitched 'water hammer'... I think I'll replace the regulator just to prove what is wrong with it...

oh dear - it's time to eat a very large portion of humble pie.. I'm embarrassed to admit that I prematurely ejaculated my diagnosis of the noise.. it turns out that it WAS in fact the radiator thermo fan (my humble apologies to JBT) - it did it again today, and this time it lasted long enough for me to get the bonnet up and get my hands on the offender.. Turns out it's the secondhand fan I fitted along time ago, giving up the ghost. With the bonnet up - the source of the noise is obvious, but I never had the chance before.. Because the previous owner had got air con from a laser adapted (unsuccessfully), they had wired in extra relays that let the thermos kick in at odd times, when they shouldn't (so that's the next job to fix).. so that's my excuse for getting it wrong.. the engine was cold when it squeeled last time.. I thought I'd put it on the forum, in case it helps someone else.. so the beer actually goes to JBT - thanks mate... cheers Drek

You just got to love a bearing squeal