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I've had my 02 M5 for about two weeks now and got a SES light the other day. I took it into the dealer and they say it needed a new breather valve which they have ordered and are repairing under warranty. My question is does the faulty breather value affect performance in any way? I did a search here and one thread claims to not change performance, but my service tech said that the breather valve would definitely change performance. I thought it was fast before, but would be very happy if it comes back even faster. :1:
 

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I think you're right, nobody knows. I've never seen reports on this before.

There was a report that the S62 will consume more oil if the breather isn't working, but that may not translate into a performance problem.

The S62 doesn't have a conventional PCV (Positive Crankcase Ventilation) system - there's no intake manifold to provide vacuum, so it's vented more like a motorcycle, where the crankcase is vented to the intake plenum at atmospheric pressure through a pair of hoses and oil-separators. A blockage would build up pressure in the crankcase, but it wouldn't necessarily affect the way the engine actually runs.

Cheers
JJ
 

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The system is much as it has explained.

The crankcase vacuum comes from the two valve covers draw through the oil separators and then any oil that is collected free drains back to the pan through two ports, one in the driver’s side (on left hand drive cars) head and the other down a tube located in the front of the block located in the pan. Then if by chance some oil gets through and is drawn into the lower plenum there are recessed passages and a cross-over tube located at the rear designed to collect and direct it back to the pan rather than into the idle control valve. Hence the reasons there is a protruding tube rather than simply a hole located inside the lower plenum from which the idle control valve draws its air from.

As for whether a plugged oil separator could be measured through loss of power, I do not think so. If by chance the oil separators were plugged which by design is very difficult you would experience things such as rear main seal leak…….. maybe even a valve cover leak with high emphasis on the area around the VANOs area, and possibly higher oil consumption…….. if the later was sufficient enough to cause ridiculous amounts of oil to be burned then yes, I suppose the car would be down on power……for this to happen I would expect that commodities such as O2 sensors and cats would be in jeopardy too.

Take care

Shadowman
 

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The oil separator & breather assembly is a known problem on sister 4.4L V8. This may or may not apply to S62, but I imagine the system differs. The 4.4L tends to build up crud and build positive pressure in the crankcase and this can blow out seals. The rear main is the first to become affected. A slightly plugged system tends to show symptoms in a severe duty environment such as a Driver's Ed Track event. In some cases, the valve can become stuck open with loosensed crud and this causes the motor to gulp some oil on startup and blow smoke. I have heard that salvage yards are incorrectly diagnosing 4.4L 540i and 740i motors as being worn out or bad when the oil separator valve is stuck. In single Vanos M62TU 4.4L, the situation is even more serious in colder areas where frozen condensate in the system can totally plug the breather in cold weather and the valve covers will grenade (explode). BMW has had the arrogance to blame the customer for too many short trips (lol).
 

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Catastrophic engine failures due to ice-plugged crank-case ventilation causing overpressure in the crankcase and in turn rupture of the oil-pan is also known in hi-efficiency aviation diesel engines for sport planes.
These run much cooler under the engin cowl, compared to AVGAS fueld otto engines, so things that normally never have ice-problems sometimes get troubles.

So to sum it up, well working crank-case ventilation is vital.

David
 
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