A few months ago the 94 940 turbo started to run with an engine growl upon acceleration -- plus when the car came to a halt there was a peculiar metallic whirring sound, winding down as the car stops.

I diagnosed a worn-out turbo. And since then I have installed a super refurbished turbo (standard, stock Mitsubishi TD40) -- started the car this morning (Happy Thanksgiving!) -- and note that the growling and whirring sounds persist (Ehhhh ...)

So now I’m wondering if my diagnosis of the original issue was wrong(i.e. these sounds are not turbo related) – or whether the turbo itself is not being served properly (and the sounds I am hearing are of a “suffering” turbo). I was very careful and took my time at every step, but did not end up replacing the oil line. I did however remove and inspect the oil line and cleaned it thoroughly twice with brake cleaner fluid. I called parts supplier IPD, they said the wait time for a new oil line from Volvo would be 5 weeks – but if the original line looked OK, that it could be reused. So I did so. Now I wonder whether the problem is oil starvation to the turbo. How could I test this? Just unbolt the banjo bolt, start the car and observe the oil flow?

I'm on the point of driving over to Volvo for their diagnosis (-- what a capitulation!) -- but I'm not completely sure I'd have any confidence in it -- they have made misdiagnoses in the past. Does anyone have any comments that could be helpful here?