Help me diagnose strange noise

[Kozzy]

To keep things simple I will list the symptoms of the noise:

- Noise best described as a ticking noise, very similar to engine knock but slightly 'softer'
- Noise starts at around 15 MPH and is not audible below this
- It does not change pitch, volume or frequency. Once the noise starts it stays exactly the same
- The noise is the same despite engine speed or road speed, whether or not in gear, with or without brakes on
- Noise does not change going up or downhill or over bumps etc or with varying degrees of steering lock
- Can only really hear the noise with the window down and can hear the noise 'reflected' off parked cars etc as I pass them
- Nothing has changed with the car in around 6 months and the car is always run on Shell VPower, the noise has lasted over 2 tanks of fuel

This is a very odd noise and I have only noticed it over the last week or so (may have started sooner but only recently started driving with the windows down again).
Because of the constant nature of the noise I had wondered if it could be something electrical, alternator for example?

The car: '98 version 4 STi Type R

(also posted on scoobynet)

[RB Will]

how often are the ticks? few a second, constant or every few secs/ now and again

[cheesesliceking]

Not sure if the alternator speed is constant but it might be an idea to take the alt drive belt off and see if the noise still occurs, obviously this would stop the battery charging etc so not a long term solution just more to see if its the alt.

Might be a rubbish idea, but if it were me id give it a try

[RB Will]

Im no mechanic, just offering ideas. Would the AC compressor or water pump run at a constant speed?

[Kozzy]

I guess the ticks are around 3-4 a second and constant after the car has got moving. My instinct was something like the alternator but I don't know if it is constant speed. Your idea of removing the drive belt would probably rule this possibility out quite quick so will give that a try in a bit.

While searching around others seem to have had similar symptoms that pointed to a loud boost solenoid. Do the solenoid acts regularly? I would have thought they would change based on throttled position / boost? My noise is very regular.

Edit to add: RBWill, they do seem like possible candidates too now, I can see me pulling all of the drive belts off at this rate :S

Edited by Kozzy on Tuesday 5th February 13:40

[japgt]

Alternator, woodruff key on pulley, injectors, boost solenoid, could be something just loose and flapping about possibly

[cheesesliceking]

Hope you get to the bottom of it.

[Kozzy]

Well I've had a bit of a look under the bonnet and I am almost 100% sure it's not the boost solenoid, it is clicking away quite quietly. The noise appears to be coming from the right of the engine somewhere beneath the alternator (again alternator seems to be making no noise). Could this be a bearing in the water pump?

I will have a proper look under the bonnet over the weekend and maybe even record a short vid to see if that can help shed some light.

[japgt]

Could be, could one of the belts be freyed and ticking as its going round bearing on alternator pulley noisy injector on right bank.

[Lee UK]

I have had something similar on various cars and I always thought it was the wire on the brake pads, it was probably something on the tyres.
I never noticed much of a difference in tone or speed and never found the cause but I think it disappeared after a while

[ABugeye4Tom]

Sounds crazy metal in tyre tread?

[ScoobieWRX]

The only things under the bonnet that aren't speed dependent and could make a noise are the Electronic Boost Control Solenoid, your Turbo Wastegate or the Turbo Heat Shield.

To me it sounds like either you have a very loud EBCS clicking away, or your wastegate is chattering inside the turbo, or possibly your heat shield is rattling away.

[cheesesliceking]

ScoobieWRX said:

or possibly your heat shield is rattling away.

This, never had any kind of car before where the heat shields rattle click and tink so much.

[ScoobieWRX]

Common as.....

[cheesesliceking]

good!, dont want a ticking timb bomb

[Kozzy]

I took the car out last weekend and drove it along a quiet road where I turned the engine off and coasted from 30 to almost stationary. The noise continued long after the engine had come to a complete stop and didn't change when in/out of gear of clutch depressed or not. I am leaning more towards something actually rattling now.

I got my other half to film a (rather boring) vid of the dash so the noise could be heard and will post this up if I can't get any further.

What heat shields (and where are they located?) are likely candidates?

Cheers for the input guys, much appreciated.

Edited by Kozzy on Friday 1st March 16:25

[rhinochopig]

It could be a lose wheel nut if the ticking slowed with the car. That will cause a ticking noise. As a kid I can recall my father spending a weekend trying to source the location of the ticking noise that his landy had started with and he eventually tracked it down to a single only very slightly loose wheel-nut.

[cheesesliceking]

[quote=Kozzy]
What heat shields (and where are they located?) are likely candidates?
quote]

All of them!, sorry, but seriously, it seems all the heat shields on my Bug tick, from the turbo right back to the CAT shields.