High pitch hum - Disco sounds like a spaceship

[Jazzman]

My D2a TD5 AUTO has a high pitch hum that comes and goes. It is very loud and I cannot pin point where it is coming from. The girlfriend thinks it is coming from the back but isn't 100% sure.

It only happens at 100km/h, it doesn't matter what the RPM is. Or if in 4th or 3rd. If i put the transmission into neutral it is still there. If I put the transfer case into neutral it is still there. I cannot get the noise when parked changing the engine revs.

It sounds like the kind of noisy you would use in a movie to "beem up" something from the ground into a spaceship. This made me think possibly electrical interference, so i turned off the radio, uhf and reverse camera monitor. The climate control and GPS were already off.

I thought maybe broken exhaust stud but when I looked most of mine seem to be replaced already and none where loose.

I then thought maybe the speedo sender is electrical, but i can't imagine the speedo generating a signal that could be amplified by SOMETHING so loud.

Any ideas before I go crazy?

[Outback 1]

do you have ace if so it could be something stuck between the pipes under the car and the body
ps speedo reads off abs sensors I believe

[Jazzman]

do you have ace if so it could be something stuck between the pipes under the car and the body
ps speedo reads off abs sensors I believe

Cheers for the response. No ACE or SLS. Thanks for the speedo from ABS tip.

[Jazzman]

Actually today I had to brake really hard and late to avoid a collision. The ABS kicked in. I wouldn't have thought it would be related.
I first noticed the sound on Monday night after removing the bull bar and refitting the standard bar. I didn't hear the sound this morning on the way to work.
I didn't put the head light squirters back in the bumper bar, I wonder if it is making a similar sound to when you blow across the top of a beer bottle. Bit of a stretch though?

[EvilGTV]

Checked your driveshafts lately? If it's road speed related, pretty likely to be something between the output of the transfer case and the wheels. The stupid weights bolted to the diff or transfer case could also possibly get a resonance up from slight driveline vibrations.... Brake pads/handbrake shoes could be dragging...

[Roverlord off road spares]

time to re negotiate :wasntme: or try a warranty claim :wasntme:

Seriously though, check the plastic A pillar finishers, they can catch the wind and hum, drone, flap etc. The retaining clip lug underneath snaps with age. Are there loose. got movement?
Try putting some tape over the trim and windscreen join go for a spin and see if the noise is gone

[bob10]

One thing you can do, remove the plastic covers under the front, grab a good torch, pinch bar, and move from front to back, carefully checking everything underneath. Push, pull, prod, check all your bushes, sway bar mounts, gearbox mounts, etc, use the pinch bar to check the joints in your driveshafts. If your vehicle is dirty underneath, hit it with the pressure washer. You may find leaks you didn't know you had. Or a worn bush, setting up a resonance at 100 KPH. Or not. Either way, under the D2 is a thing of beauty, Bob :)

[ballbag]

Ah Bob, a man who appreciates the finer trappings in life!


Speed not rpm related so mechanically can only be between gear box and tyres, or air resistance somewhere.

Roof racks?
Sun roof?
A pillar dress covers?
Plastic air foil between bumper bar and radiator?
Head hanging out window?

[bob10]

Snorkle? Bob

[Jazzman]

Thanks gents. I'll have a look at all suggestions. Don't have a snorkel, yet.

[Tombie]

So when was the last time you checked all your fluid levels?

Greased your drive shafts?

Start with basics :cool:

[bob10]

So when was the last time you checked all your fluid levels?

Greased your drive shafts?

Start with basics :cool:
Rear diff? Bob

[Roverlord off road spares]

Shane, On Drivers side Dash near your mirror switch there is a little grille next to it (just to the left.)
Behind that grille is a little fan that circulates the cabin air to a sensor for climate control. These do get crud in them and can make a funny noise and you don't know where the noise is coming from
regards,
Mario

[Discofever]

I had a similar issue on my D1 - loud hum @ 100km. Took me ages to pinpoint it until I finally took the roof rack and awning off -noise gone.

[trog]

The plastic A-piller trim was not seated properly , nor was the snorkle mount and the front rain gutter . ( the little 90 degree bend piece ) once all refitted after a wind screen replacement not only a reduction in rattle , but no wind related noise at speed.

[Jazzman]

Shane, On Drivers side Dash near your mirror switch there is a little grille next to it (just to the left.)
Behind that grille is a little fan that circulates the cabin air to a sensor for climate control. These do get crud in them and can make a funny noise and you don't know where the noise is coming from
regards,
Mario

This is the kind of thing i expected it to be. I'll have a look tomorrow.

[Jazzman]

I had a similar issue on my D1 - loud hum @ 100km. Took me ages to pinpoint it until I finally took the roof rack and awning off -noise gone.

I thought it could be this too, but I've had my awning, roof bars and roof top tent fitted many times without this noise. I guess it is still possible but ruled it out early as it had not done it before.

[Jazzman]

The plastic A-piller trim was not seated properly , nor was the snorkle mount and the front rain gutter . ( the little 90 degree bend piece ) once all refitted after a wind screen replacement not only a reduction in rattle , but no wind related noise at speed.

Interesting, my 90 degree plastic bits in the roof gutter are all cracked.

[Roverlord off road spares]

Have you removed roof rack and roof tent top off and tried?

[Jazzman]

Have you removed roof rack and roof tent top off and tried?

Not yet.

[Roverlord off road spares]

Shane another long shot, but the wind deflector on the drivers side windscreen wiper, remove it and see if the noise goes.
cheers,
Mario

[Jazzman]

I think I've worked out what was making the noise.

Landrover Discovery 1 2 1992 2004 Adjustable Roof Racks | eBay (http://www.ebay.com.au/itm/161207555647'ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)

After removing the roof top tent, instrument fuse and everything else i've already mentioned.

I took the roof rails off and no more noise. Must say i'm disappointed, i need them :(

I'll drive around some more tomorrow and see if the noise comes back or not.

[Jazzman]

OK it is confirmed. The roof rails are the culprit. DAMN!

[bee utey]

OK it is confirmed. The roof rails are the culprit. DAMN!
Fill the channels of the roof bars with bitumen impregnated (BIP) foam, available from any builders hardware, e.g. Stratco. It's used in places like expansion joints and will last a fair while out in the open.

[Tombie]

Sellers Space invader will sort a tube too

[Jazzman]

Fill the channels of the roof bars with bitumen impregnated (BIP) foam, available from any builders hardware, e.g. Stratco. It's used in places like expansion joints and will last a fair while out in the open.

Thanks for the advice. I thought maybe filling the ends would solve the issue. But would probably need to fill the whole channel.

I ended up buying a new full length roof rack for $280. Factory second.