Thread: buzzing noise
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      02-02-2013, 12:04 AM   #14
Stupid Idiot
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Drives: E90 335i & C6 Grand Sport
Join Date: May 2009
Location: Santa Barbara

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Originally Posted by München View Post
Performing that is when your bleeding the system and you activate the pump to "self" bleed the system, it does not do this when you shut off / seize engine operation, this will not perform this operation after driviing the car at a normal basis.

Correct me if im I wrong....the turbochargers "thrust bearing" floats on engine oil right? so if you are driving to your destination and are on boost by the time your reach your destination and shut off the engine, the oil pump is no longer pumping oil....causing coking and people that follow the CBS on the car and believe that the engine oil will last 15000.00 miles is main receipe of early turbo failure.

Most Turbocharged cars have the oil feed for the turbo's on top and return oil line below ( vertically) and coolant banjo fittings for coolant run horizontally
crossflow cooling.

Mini Coopers that are Turbocharged have the auxillary water pumps.... I have been wrong, so please enlighten us where is this Auxillary Water Pump on MY N54 E90 located at, since we work on these cars day in and day out.

The N54 cars don't have any auxiliary water pumps. It just has one (1) powerful electric coolant pump that it uses for circulating coolant for the regular cooling system, the heater, and the turbos. The DME has programming logic that will run the pump after engine shutdown under certain conditions. I didn't engineer it, so I can't tell you when exactly. Here are a couple clips from the BMW Cooling system technical training info:

The electric coolant pump on the N54 engine features an after-running function to carry
away the heat build-up from the turbochargers after the engine has been shut down.

After-running of electric coolant pump =
improved heat dissipation from engine switch off
point. Allows protection of turbochargers by
reduced oil “coking” during heat soak.

Those are straight from BMW North America's training info, for what it's worth.

As far as the cooling system bleed procedure -- yes, it's intended use is to bleed the system after a repair. I was just telling the OP to run the bleed procedure and listen to the sound the pump makes. Since it will run through it's various speeds with the engine "off", it is very easy to hear and could help him determine if his intermittent noise is in fact his water pump. That's all. It's really hard to hear the water pump with the engine running.