Turbocharger rattle/knock?

[greekph]

I have a question for the knowledgeable people here: My WRX, '04 model, 300k kms, totally stock, developed a strange rattle recently. It sounds like rod knock but not as loud. It happens on steady throttle and when I let go of the gas pedal, from around idle to 2-2.5 k rpm. Other than that everything is normal, the engine pulls normally, no smoke from exhaust, only smoke from outside the turbo.

In the beginning I thought "that's it", considering the mileage on the engine. Upon closer inspection (long screwdriver on the ear) it seems that the noise is coming from the turbo itself and not from the engine block. Disconnecting the injectors sequentially did not change the noise much. This together with the increased quantity of oil seeping out of the intake side on the turbo has me thinking that maybe I am lucky and it's just the turbo that is failing. Heat shields and other obvious stuff checked ok.

Does anyone have any similar experience and if so, what was the problem? Sorry for the long post, but an internal engine failure will mean the end of the road for the old girl

[texaxile]

Here's a shot in the dark, it might not be the turbo but instead one of the CATs might have broken up inside the exhaust housing, either on the up pipe ( if it's a pre 06) or downpipe .

I've seen this happen before (not on a scoob though) and the rattle appeared at a certain rev range, sounded very metallic and ominous, turned out to be a broken cat.

If the turbos on it's way out, there's often forward and backward movement in the shaft indicating the thrust bearing is knackered, along with oil consumption and smoke. Oil pushing past the seals is just that, another indication of a worn unit but I can't say I've heard a turbo rattling through wear before.