scott22

Hi,

My STI (97 reg) has developed a whirring noise when accelerating up to 3,500 revs... it 'whirrs' (or for want of a better description, 'hums') for a split second then seems to drive through it. This happens mainly in 3rd gear.

Has anyone had a similar thing happen or any ideas what the cause might be?

Cheers

Scott

BDF

Sounds exactly like what is happening on my car. See my posting titled 'Exhaust manifold heatshields'.
It sounds like an 'oooooh' noise. - lasts from about 3500-4000rpm. At first it happened infrequently - I asked the dealer to check it out when it was in for a service - they couldn't replicate it. Since then it has become progressively more persistent and seems to do it all the time between said revs (once the car is warmed through). I'm considering removing the manifold heatshields to see if it cures the problem. I'm loathed to do it ,though without the replacement parts cos i'll never get the old rusty ones back on as you just know they'll have to be cut off due to rusted fasteners.

RT

I get the exact same thing. Had it from day 1 of ownership, therefore don't think that mine's a rust problem. Happens bet 3600-4000rpm, every gear, any speed, clutch in or out.

Given up chasing it down, car doesn't seem to be affected in any way. JDM MY01 STI RA 26000kms.

BDF

Just been reading some literature on the subject from the SIDC. I now believe the problem to be a faulty blow off valve (common on 97 cars). The sound is generated as a result of the valve not closing properly.
I presume this means that valuable boost pressure is being lost.

scott22

Cheers for the replies lads - taking it to the local Subaru dealer tomorrow for them to check it out...

Just out of curiosity, how much is a blow off valve??

I'll let you know how I get on tomorrow.

Scott

BDF

Blow off valves (after market)...About 100 notes after preliminary enquiries.

RT

BDF:
does yours happen under any particular load conditions, or does it happen all the time at those revs?
ie not dependant on moving, stationary, gear position, clutch position etc.

tks.

BDF

It happens only under load - on boost, at any speed.It stops as soon as I back off the throttle, when I re-apply the throttle it comes back but tails off and stops at around 4000rpm.
I have just ordered a Bailey recirculating dump valve as I am 90% sure that the little plastic original jobbie is not shutting properly when at moderate boost levels.
I'll post the results once it's fitted.

RT

Sounds like the BOV then. Mine is different - happens under load or no-load.

scott22

Update on 'humming' noise...

After visiting my Scooby doctor on Friday, I think we're getting somewhere... I told them what the noise sounded like (i.e. someone blowing across the top of a bottle) and after taking the car out on a road test, he said it was the air inlet valve which wasn't opening properly. The part is around £70 apparantly - this dealer's in Shipston-on-Stour (Nr. Stratford up on Avon) and they service imports. I asked if it was a common fault on the '97 reg, and they said they've only ever replaced 2 as far as they knew, however it's not to say that some drivers are still driving their scoobies with the noise and don't know about it!

Hope this is some help to those of you experiencing a similar problem.

Scott

RT

What exactly is this "Air Inlet Valve"?

BDF

Replaced my BOV - Problem solved.