Comments on my strange noises sought !

[Epic pooh]

Hi Everyone,

Hoping the collective wisdom could shed some light (or speculate from experience) on two odd noises I have:

1. is a kind of 'woomp woomp woomp' noise that only happens under load - the noise starts under throttle and ceases when throttle is lifted and does not increase under heavy acceleration (ie. it is present under throttle at the same tone/volume irrespective of throttle position). It's audible in the cabin to my trained ears (but not so much to the mechanic), it's normally fairly quiet but when towing (1.5t) and heavily laden it has been quite loud. Can rule out: exhaust, wheel bearings. Suspects: driveshaft bearing ? gearbox (has no symptoms that would point to the box) ? some other bearing somewhere ?

2. a buzzing noise in the cabin when starting up, continues for up to 10 seconds, used to do it only when cold but now does it on most start ups. Kind of sounds like a dodgy computer fan but faster. Does not matter if the car has a/c on or off when starting noise still present. I do have a dodgy a/c compressor but I do not think that is the noise as it appears to come from the cabin. Have logged seat motor faults (my seat memory computer needs changing) but I don't think the noise is from the seat motor.

Any comments or speculation would be very gratefully received !

Vehicle is '05 V8 HSE D3.

Cheers,
Mick

[scarry]

Item one,have you ruled out an out of round or damaged tyre?
Often will cause issues only under load.

Item two,can't help you,dunno??

[Epic pooh]

Cant definitively rule out tyre issues - my GG AT's are oddly worn and are generally annoying from a noise point of view, but to me this does not sound like tyre noise. Would an out of round tyre only make noise under load (acceleration) and cease when throttle is lifted ?

[ADMIRAL]

Item one,have you ruled out an out of round or damaged tyre?
Often will cause issues only under load.

Item two,can't help you,dunno??

Ditto. Go tyres first for the noise. No idea on the second item. Check if it is a referred noise. Open the bonnet and have someone start the motor.

[90 Rangie]

For number 1 Maybe worth dropping oil out of both diffs. Could be a diff type noise.

[Mungus]

For Number 1 - I had a similar noise in my Commodore. Finally found the culprit was the fuel rails; actually a flex hose connecting to the fuel rails. When I grabbed the hose the pulsating woomp noise stopped. Very hard to hear, but I hear all sorts of weird noises that no-one else does.

[Epic pooh]

I suspected diff noise when it first occurred (this has been going on noticably for about 9 months), two mechanics say not and both blamed exhaust noise, one mechanic has a view that the large centre muffler is on its way out (duly checked by exhaust guy who didn't agree and after a road test he blamed a driveline issue but was far from certain)

All diff and transfer case oils were changed about 18mths ago and they were all in very good condition when taken out. Trans has had a steel pan fitted and oil changed at the same time, its oil was also good. I have no vibrations or any kind of driveline clunks or suchlike.

New tyres are on the cards in the very near future - but these ones have had multiple rotations and balance correctly, I am sure one of the rears is not right (high speed vibration when on front).

For the second noise, I've done a lot of 'turn this on' 'turn this off' when starting (air, stereo, rear air, seat in different position) - at first I thought it may have been my new AMK compressor, but it doesn't seem to be that (different pitch and not aligned with compressor cycles). Oddly, after a recent 1500km drive towing, it is now making this buzzing noise on every start up (whereas before it was only first start of the day).

Thanks all and keep the ideas coming !! :)

[ADMIRAL]

Eric,

The tyres can be balanced correctly, but if they are out of round ( eccentric ) or the rim is bent, the vibration will still be there.

[CaverD3]

Buzzing noise could be the LP fuel pump?

[90 Rangie]

The oil in my front diff was fine when changed at 80,000km and had plenty of metal at 90,000. only small amount of oil to drain to check.

[Epic pooh]

Thanks guys - tyres are definately on the short term agenda ... just need to decide which ones (thinking of a return to Pirelli Scorpion Zero or trying Scorpion ATR).

You're right 90Rangie, there is not a lot of oil to change, I might do that again and see what comes out.

The fuel pump suggestion is a good one Caver - mine is a V8 petrol so only have the in tank pump which is in proximity to where I perceive the noise to be coming from. Might shove my gopro (good mic) up in it's general direction and start it up to see if that is the source.

cheers
mick

[Epic pooh]

I was taking a look around today (changing memory seat ECU and bonnet struts) and discovered this very obvious crack / failure to seal in my exhaust ... suspect this has something to do with noise under load and possibly the other noise too ... off to the muffler guy on monday so hopefully that will nail one of them !

Also pic of new seat computer ... now my mirrors return to their normal position after reversing (has been bothering me for years) !