Weird Noise

[RicKDoG]

i have an auto r33 gts and wen the car is cold at about 2800rpm it makes a weird noise like a flutter noise i got da muffler changed and exhaust checked out but was told it all seems fine after the car is warm it doesnt really do it wondering if ne knows wot it could be

[Redback]

not a timing belt..... just having a stab in the dark here. or a really farked thrust bearing.

could be turbo even.. have ya chucked your head under th bonet to see if you can hear where it comes from

[RicKDoG]

not a turbo it doesnt sound as if its comin from the engine more of the exhaust but that was checked so i dnt think it is that it only does it if im driving not if i just sit there and rev it, it has to be in drive

[The Dan]

  Redback said:

not a timing belt..... just having a stab in the dark here. or a really farked thrust bearing.

could be turbo even.. have ya chucked your head under th bonet to see if you can hear where it comes from

<{POST_SNAPBACK}>

Thrust bearing?

It's an auto.

Does it make the sound while free revving (neutral) it or does it have to be under load? (driving down the street)

[RicKDoG]

has to be driving

[RicKDoG]

and yeah is auto

[Rolls]

catalytic convertor maybe? when they are shagged they can rattle make or make weird vibrations.

[RicKDoG]

YEAH AT FIRST I THOUGHT IT WAS SOMETHIN LIKE THE CAT BUT ITS BEEN CHECKED BY 2 DIFFERENT MECHANICS AND THEY RECKON THE EXHAUST IS FINE MAYBE THERE MISSED SOMETHIN WEN THE CAR IS WARMED UP ITS FINE SO WOT EVA IT IS PROBABLY EXPANDS OR SOMETHIN IN THE HEAT TO STOP IT BUT ITS WEIRD HOW IT ONLY DOES IT UNDERLOAD NOT WEN JUST FREE REVING IT

[The Dan]

Is there any way you could be a little more specific on the noise. 90% of the time when I am trying to sort out a problem for a customer they are saying 'bang' when really it's a 'click' or 'rattle' when it's a 'squeak'. Can you describe it any better than fluttering and have you gone for a drive with someone to try and locate the position of the noise a little better.

When they checked the exhaust, did they check your manifold gasket (often missed on an exhaust inspection).

Easiest way to test it is get a rag big enough to fold up and put over your exhaust tip. Then get someone to block the exhaust in 2 second intervals while you stay up the front and listen for any leaks. You will hear it start to hiss when your friend blocks the end as the pressure builds up quite quickly. This noise may be present while the engine is cold because everything hasn't expanded yet. Once the heat get's through it and the manifold expands a little, it will seal off the leak.

Go check it out - easy to do at home and will rule out the exhaust.

If it's the cat, all you gotta do is get half under the car and give it a bash, if it rattles - it's rooted. Only a rattling cat will make noises while driving.

[RicKDoG]

ILL GIVE THAT A TRY THE ACTUAL NOISE SOUNDS AS IFS ITS COMIN FROM THE MUFFLER BUT I HAD THAT CHANGED AND DIDNT STOP IT ITS KIND OF A RATTLE FLUTTER IF THAT MAKES SENSE ITS WEIRD HOW IT ONLY DOES IT AT A CERTAIN REV PROB BOUT 2800 AND PROB STOPS WEN I GO PAST 2900-3000

[The Dan]

And the result of you leak check that I described before?

It's not something silly like the stock heatshielding on the exhaust buzzing. When the insulator falls apart underneath them they get this tinny rattle.

[RicKDoG]

i didnt hear anything wen doin the leak test it all seemed fine im thinkin there is probably somethin wrong wif 1 da cat convertor but wen its been looked at its been missed