Please help...drumming noise...

[jkseries]

This is doing my nut in and I can't work out where it's coming from.

I get a drumming noise from the engine bay somewhere on my 300tdi es auto

It only happens when the engine is under load at 3000rpm. There is no sign of this noise under normal driving conditions just up hill foot down driving brings it on.

To recreate the noise I've spent the day sat on a slight incline with the car in 'd' hand and foot brakes on and then rev up to 300rpm.

The noise will come in like a drumming and then die off after about 20sec.

I've checked hoses. Vacuum pipes. Head gasket, rocker gasket. Inlet and exhaust gaskets.

It won't do it just by revving the engine on the flat.

There doesn't seem to be any loss of power.

I must be missing something special.

I'm thinking it must be turbo related as it comes in the power band of the turbo.  So had hoses off there as well and there was no change in volume or severity.

Any advice of where to look next is VERY greatly received.

Thanks

James

[lee celtic]

Have you had a look underneath to see if any of the mounting rubbers on the engine or exhaust have gone ??

it might be that at that rev the harmonics of the engine match the frequency of the exhaust causing it to vibrate and hit the floor or something .

the wifes car does it if you don't rev enough when pulling off ..

also there might be a fin damaged on your fan causing the noise.

thats only two there could be more  :( good luck.

[jkseries]

Thanks Lee

A job for the morning I think.

Any more ideas anyone.