BMW E90 diesel: turbo fault, whine and loss of power
Why does the turbo on a BMW E90 diesel whine or howl and lose power?
A typical cause is play in the turbo shaft: the shaft is loose and the blades hit the housing wall. The symptom is a high-pitched whine or howl when accelerating, usually above 1500 rpm, along with a lack of power. The fix is replacing the turbo.
Is any play allowed in the turbo shaft?
There must be no play at all lengthwise. A small amount of sideways movement is considered normal, because oil pressure centres the shaft. If the shaft moves in every direction, the turbo is broken.
Is it worth buying a reconditioned turbo?
Reconditioned turbos are regarded with caution, because some of them started to screech after only about 800 km of driving. The durability of a variable geometry turbo also varies a lot from one unit to another.
What can break a turbo prematurely?
Too long an oil change interval. Oil sludge can block the joint of the turbo's oil feed pipe, leaving the bearings without lubrication. Doing the oil change and cleaning the clogging joint regularly protects the turbo.