Engine off Cabin Heat and turbo cooling question

In the N54 the electric water pump will pump coolant through the turbo to cool it and I believe that it will cool the turbo if required even with the engine off as directed by the DME. My question is that if you push the "REST" button to heat the interior of the car while the engine if off, does that also provide a manual method of cooling the turbo since it uses the coolant pump.

Originally Posted by jburke4689

In the N54 the electric water pump will pump coolant through the turbo to cool it.

Are you sure about that? I've never heard the water pump run after shutdown. Then again, I've never listened for it. I'm not questioning your knowledge, just seeking confirmation.

One nice thing about a water cooled turbo is that, if the plumbing is done correctly, the coolant will continue to circulate through the turbo via convection. So a pump may not be needed.

I live in fear of turbo coking. At some point, I plan to add an after-oiler to my car. Here's an example. http://www.racerpartswholesale.com/p...4964/Accusumps

I plan to mount it forward of the radiator, so that when I shut down, a charge of cool oil is pumped to the turbo bearings to quickly lower their temperature.

As far as your question goes, if the water pump is running, then coolant will be circulating through the turbos.

Frederic

Originally Posted by TXFred

Are you sure about that? I've never heard the water pump run after shutdown. Then again, I've never listened for it. I'm not questioning your knowledge, just seeking confirmation.

Mike Miller (Roundel) has confirmed it in a couple instances. He also says "it's very quiet". Sorry, can't remember which month/issue - they're up at my cabin.

As for whether the rest heat function's pump is the main one and will cool the turbo, don't know. My 335d has an auxiliary pump mounted on the left strut tower (about 8" below the top) that I understand is used on those (diesel) cars with the rest heat function - but then the M57 has a belt-driven pump. Can't find the aux pump on realoem.com for the 335i.

Originally Posted by jburke4689

In the N54 the electric water pump will pump coolant through the turbo to cool it and I believe that it will cool the turbo if required even with the engine off as directed by the DME. My question is that if you push the "REST" button to heat the interior of the car while the engine if off, does that also provide a manual method of cooling the turbo since it uses the coolant pump.

Yessir - there is 1 body of cooling water. But:

I've appreciated REST on many winter stops but don't remember turbos cooling then.

My cooling water can run through the turbos after a warm evening run, but there's no need for REST in that weather.

Originally Posted by floydarogers

My 335d has an auxiliary pump mounted on the left strut tower (about 8" below the top) that I understand is used on those (diesel) cars with the rest heat function - but then the M57 has a belt-driven pump. Can't find the aux pump on realoem.com for the 335i.

I looked under the hood of my 335i. There's no aux pump that I can see. The heater hoses run to the front of the engine. So I assume that Rest just activates the normal coolant pump.

Frederic

Originally Posted by TXFred

I looked under the hood of my 335i. There's no aux pump that I can see. The heater hoses run to the front of the engine. So I assume that Rest just activates the normal coolant pump.

Yup - the electric water pump.

Here is a quote from the BMW N54 Engine Management Training course on the value and advantage of the electric water pump.

Component Protection
• 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.

The schematic doesn't show any valve other than the thermostat so I guess pressing "REST" must run coolant through the turbochargers.