[r33nik]

bit of an odd one this.....when acceerating hard the other day i heard the usual whooshing noise (sorry for the terrible description) but when the revs got around 6000rpm the pitch of the noise changed into a kind of hissing noise which i can only describe as a very similar sound that an airline with an airgun makes......when the auto box changed gear the noise whent away.....

thing is the car drives exactly the same and doesnt feel any slower whilst this is happening. Ive only got the standard boost guage but that doesnt alter whilst i hear the noise......in fact the only thing bad about it is the noise for now but would really like to now what it could be and how it isnt affecting performace.

ive had a quick check over hoses and all seems well but im not exactly sure what to look for so i could have missed something.
also the car is standard with original turbo. And when idling with the bonnet up it sounds perfectly smooth with no noticable faults ?

help is appreciated as i have purchased another gts-t and want to find whats up with this one so that i can fix and sell it.

 

[bernmc]

Sounds like a small air leak on boost...? Smaller the hole, the higher the pitch, so you may not be losing much.

Can be a bugger to track down as you need the engine to be under load to build up boost to find the source of the noise...

 

[r33nik]

cheers for your help.
dont suppose you know which hoses tend to give up the ghost first or are they all as likely as each other to break.
i would rather not have to remove them all if there is one that is more likely to break first i would rather start there.

 

[Kevacky]

Could be a stud gone in the exhuast manifold, boost will still pull but it'll drag air in. Sadly i know coz my gtst started doing it. Bummer.

 

[r33nik]

was it making the same sort of noise in similar conditions to mine then.
hadnt even considered this. was only thinking along the turbo/boost probs...:uhoh:

 

[ChrisC]

Have a look at the 2 elbow hoses that go to the intercooler ( thats assuming you still have the std wing mounted one) I had a simmilar noise and it didnt appear to be loosing any power, however one hose had split on the inside of the bend, so was only visable once i had took the pipe off, and was opening up under full boost. Went like a rocket after i had replaced it. Worth a look.

 

[r33nik]

cheers i will have a look at them now

 

[mick-skyline]

have you an after market BOV i know some of them will actually allow air out while still accellorating due to a weak spring, maybe it could be down to this. just a guess though.

 

[r33nik]

no aftermarket BOV is fitted and ive checked all the hoses. I even checked the turbo for excessive play on the bearings but all seems fine...in fact the hoses look in very good condition...however it could still be this as i hear the leaks can sometimes only be visible when under pressure.

I have remebered something that might shed some more light on the problem though (well hopefully someone on here might see some significance in this...lol) the other night i had what i thought was a stone hit the underside of my car....im am wandering if perhaps it was a manifold stud as mentioned.

when driving a can fully acelerate all the way up to 80 (on a private road) with no weird noises (i guess my auto box is in 3rd gear at this point) then i start to here the air rushing / hissing noise from the nearside of the engine bay. but when it goes into fourth the sound goes away.........:crazy:

 

[Chris Wilson]

Sounds very much like a broken stud(s) on the turbo manifold to head face, or a split head to manifold gasket. Check every stud for tightness and presence. Don't OVERtighten, you may need to remove heat shields.

 

[mick-skyline]

Sounds very much like a broken stud(s) on the turbo manifold to head face, or a split head to manifold gasket. Check every stud for tightness and presence. Don't OVERtighten, you may need to remove heat shields.

yeah more than likely a stud been sheered off while driving. easy enough to do

 

[r33nik]

cheers for the advice guys i will have a look at this when i next get chance..... I bet studs that have sheared are a right sod to get out :uhoh:

 

[Chris Wilson]

They can be, some of the Skyline specialists, Rod Bell for certain, have special tooling to ensure concentric drilling out of the broken studs, and accurate helicoiling of the new stud holes There are mods that can be made to help prevent a recurrence of this problem, too.

 

[SARU]

There are mods that can be made to help prevent a recurrence of this problem, too.

such as ?

 

[Grinder]

This sounds like the noise my GTT made a while back - was found to be due to turbo-to-manifold gasket expiring. Gasket replaced, £300 later all sorted.

 

[Poirot]

such as ?

slotting helps on the manifolds, most come slotted as stock

i presume thats what he ment?

 

[r33nik]

i wont be able to have a proper look at the manifold and fixings untill the weekend but something is confusing me as ive noticed that the speed at which the noise happens has lowered by 5-10 mph and it doesnt happen right till the end of third gear now unlike how it was a couple of days ago. I tried the car again yesterday and i cant get it to make the noise in 1st or second on full boost and it doesnt happen in 4th (auto gearbox).....at first i thought its the lower revs in fourth but why wouldnt it do it in 1st and 2nd.........

listening to it again it sound like the wastegate noise is the one that changes pitch into the air hissing noise but i could be wrong....

 

[r33nik]

had another listen with the windows down and it does make the noise in first and second gear its just not so loud.... drive it normally and theres no weird noises. Its only on full acceleration that i hear the air hissing noise.

 

[R33 lee]

I think i have the same.....

(manual gearbox)
under low and easy acceleration - wife driving i hear nothing throught the rev range, when i drive under harder acceleration theres a constant whine/whoos from 4000-5000 until i change gear, happens throught the gear range, have checked under the bonnet and i thinkg its due to my standard dump valve recirculating the pressure - weak spring (sounds like its coming from my induction kit)

am looking for an upgrade dump valve at present but it might be a weak spring bud if you dont hear anything under low acceleration

Cheers

lee

 

[r33nik]

sounds very similar lee....when i had the original air filter box on all was quite but about a year and a half ago i fitted an induction kit and ever since then you can here an air rushing ( though normal ) noise sort of behind the glovebox ( wastegate ) and its that thats changing pitch at the 6000 ish rev range before it changes gear (or so it sounds)....it suddenly changes from a whooshing air noise to a much louder air rushing noise then dissapears after gear change then comes back when revs get back up to 6000.
Thing is its sounded fine for 2 years then one time i started it i heard the noise straight away.....

thing is though can a spring weaken just like that cos i would have expected it to get slightly worse each time gradually making more noise......hope my descriptions make sense lol.