Why does the turbo of my diesel get so hot?

I own a MINI Coupe 2.0 diesel and now and again I get a smoke smell like burning oil coming from around the turbo. I took it back to the garage and they said it was a leaking rocker cover gasket. I took the car away and three weeks later the same thing occurred but with the engine fan on for 15 mins after the engine was switched off and bubbling water in the expansion tank. What is wrong?

Asked on 20 July 2018 by Andy

Answered by Honest John
I think that what has happened here is the engine has been switched off directly too many times when the turbo was still almost red hot. This has then carbonised the oil in the turbo bearing oil feed and oil return pipes, restricting the flow of oil to the turbo bearing making the overheating even worse and because the turbo is also watercooled it has boiled the coolant passing through it. leading to overheating of the engine.
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