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

 

boost solenoid? They can be rather loud

 

Was thinking the same thing, its mounted to the drivers inner bay on the strut turret, they have been known to make a noise if there getting on a bit, but probably still fully functional, have you got a boost gauge fitted? If so when does it start to make the noise with regards to boost? Does it do it constantly over 15mph regardless if you have your foot on the throttle or are off boost light cruising?

 

Interesting, I hope it is something like that. The noise doesn't seem to get any louder or more frequent with higher RPM. Would the solenoid clicking be a fairly constant noise regardless of throttle or boost?

Edit to add: The noise does seem to be louder on the driver's side but I have only noticed it when the car is moving around 15+ MPH. It doesn't seem to get louder or faster with increased throttle. I do have a boost gauge and the boost seems to be ok, peaking at around 1.2 and settling at 1.1 full throttle (at this point can't hear the noise as the car is pretty loud at full chat).

 

Yeap they can do.

Try giving it a clean

Disconnect the solenoid pipes
Connect the green test connectors under dash and turn the ignition on (This will make the solenoid pulse)
Spray some carb cleaner into the solenoid. You'll probably find a load of black crud will come out.

 

Thanks Mark, I shall give this a go. Should at least be a simple thing to rule out and can do nothing but good anyway.

 

Could it be something daft like a nail or a bolt stuck in the tread of your tire?
That would make audible ticking type noise, louder when your window is down and quicker when you accelerate.

 

This noise is fairly constant, it doesn't get louder or go faster with revs, speed, throttle position or boost.

It has to be something capable of making a fairly 'steady' constant noise. Hence my initial thought was a drive belt for something like the alternator (as I believe this is likely to stay constant).

Other people have pointed to a gunked-up boost solenoid, which is something that should be easy to rule out or indeed be the culprit.

 

alternator etc... would change with engine speed as they run off the crank pulley.

 

man! it could be many things, my input would be timming belt pulley or idle control valve the one they change sometimes when belt is done.????

 

check if the noise changes if you slightly push or pull the gear stick mine has a bit of a tic/click couldn't figure it out for months