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Disco Td5 chirruping / squealing noise on overrun


DaveR

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Very strange noise this one. The noise sounds exactly like a cicada or cricket as featured on all the best films in the tropics! Fomr the drivers seat it sounds as tho it is coming from high up in the passenger footwell.

The noise doesn't always happen, but once it does start it never stops for that journey.

The sound disappears totally on acceleration and when moving the steering wheel from the straight ahead position.

The sound is only there when the car is moving and on the overrun or during braking. When stationary but with the engine running, it disappears.

Everything works fine and there are no error codes anywhere!

Baffled. What do you think it is??

Cheers

Dave

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You didn't say if the noise characteristics change with rpm or speed so I presume it doesn't.

Could be from the heater fan. In case you keep the climate control on auto, swich it to manual and cycle through the steps next time you can hear the noise to see if the fan speed has any influence.

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Vougese39 - so why would the noise disappear instantly with just a light touch on the accelerator and similarly reappear when I lift off? Still baffled! Thanks for your reply though.

Cipx2 - the noise is at the same pitch regardless of engine or road speed. It's present even if AC is switched right off.

My money is on something to do with the ABS manifold as it sounds as if it's in about the right place, or the PAS pump but can't explain why only present on overrun or braking.....

Cheers the noo

Dave

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This may sound daft but this reminds me of a weird noise in my TD5 I was chasing for weeks.

The final clue was that it would go away if I held the gear lever.

It turned out that a biro had fallen down a hole in the gear stick gaitor and was vibrating against the bottom of the metal gear stick . The nib bit of the biro was metal which made it worse.

Really glad to find it as it was doing my mind in :D

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I don't think this has something to do with ABS but you can pull the fuse when it makes the noise and see if it stops.

What transmission does it have, auto or manual?

One thing you can try is find a very steep incline like an underground garage entrance, road bank etc and place the vehicle nose down at different angles. This would simulate the inertia when braking/overrun to a certain degree and it might give you the chance to hear the noise when stationay so you can investigate under the dash/bonnet etc.

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I'll guess at exhaust manifold gasket. Reason is that these can chirp like a tweety bird when not quite sealing right. Reason for only doing it on overrun is to do with the engine leaning in the opposite direction to when accelerating. The exhaust is fixed and the engine moves causing gasket to fail causing chirping. Check engine mounts as well while your at it. Excessive movement from the mounts will cause this to kepp happening.

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  • 2 weeks later...

I've recently had exactly the same noise with my 220000 miles + TD5. It was in and out of the workshop for weeks while I checked everything out. Heater fan, hoses, blown joints were all suspects before I tracked it down to end float in the turbo. Changed it for a cheapish Craddock one problem solved! Try that before you set about demolishing everything else!

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