owner of this 2007 BMW 520d came to us complaining that it had suddenly lost power. At first, he thought it was the automatic transmission causing the problem, but after we took the car for a test-drive we realised that selecting gears manually gave no better performance.
Our first thought was that perhaps the diesel particulate filter had become clogged and needed regenerating, but this operation made no difference. Removing the air inlet ducting from the turbo, we were able to confirm that the rotor was not rotating – in fact, it had locked solid!
Reporting our findings to the owner, he suddenly remembered that there had been a whining noise for a while, which had later disappeared. He also had no memory of changing the oil and filter. This was the reason he was now going to have to pay out for a new turbo.
While fitting the new turbo and oil supply pipe, we also changed the oil and filter, discovering that the oil filter was in a very gunky state. With a caution to the owner that more care over his oil changes was needed, the Beemer was handed back with full power restored.
The turbo impeller was seized solid, impeding the air flow.