The BMW Oiling System: sketches and descriptions
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oilsketch.htm
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The above sketch is of the EARLY oiling system.... which comes from the BMW Factory Service manual  This is a photograph taken of a double page of the BMW Factory Service Manual.  All the airheads from the /5 have a similar system....but changes were made in 1980, those changes are shown much further down this page.

EARLY system, through about 1979:

Oil is also returned to the sump by the amount escaping from bearings clearances.

Later system (from approximately 1980):

  In '1980', BMW changed the oiling system internally in the engine casting.  BMW re-routed the oil so it now went directly from the filter to the front crankshaft bearing.  It passed by the camshaft flange, via an angled path to it, on its way there.  This change was incorporated at various VIN numbers....that is, it was phased into production.  NOTE:  because of that phase in, certain swapping of engine castings/components might require some modification (front main bearing cap, for instance), and the information is in a bulletin from BMW, which I have on fiche.  The phase in occurred as follows:

R65, phased in at 6381867
R80/7, phased in at 6126171
R100T, phased in at 6170415
R100S, phased in at 6165103
R100RS, phased in at 6185422
R100RT, phased in at 6196045

NOTE:   BMW had the crankcase identified when those changes were phased in.   The CLUTCH side of the engine casting has a triangle with an N in the center of it....this is cast-into the crankcase there.   This mark is the standard Alcan mark.

 OIL PAN:  The oil pan has been changed a few times over the years.  First to deepen it half an inch to give additional room for crankcase blowby and normal operational pressures; then for more capacity (and the drain moved to the rear).  All are interchangeable on fit, as they all have 14 bolts in the same place.  The later one is better.  There is an article on this website that has information on dipsticks and fitting the pan gasket, which must NOT have sealant applied.  The cork gaskets of the old days are NLA.    Do NOT over-torque the bolts (I don't go over about 6 footpounds, and actually do it by FEEL), and tighten them quite evenly all around.   Recheck tightness after a few rides.  Do NOT over-tighten!  Whenever the pan is off, check the bolts for the oil strainer pickup.  Check the pickup parts, especially the earlier pickup connection area, for cracking.  

   MORE:   In 1977 BMW enlarged the oil pan capacity.   In 1981 BMW made changes to the oil pan AND the pickup.  There had been a few instances of the all-steel pickup tube assembly cracking, which often meant sucking air, not oil.  BMW went to a dual-piece pickup and aluminum adapter with 2 bolts, etc.   Use Loctite BLUE on those clean and dried threads when assembling (and fresh gaskets too!).   The enlarged (again!) pan now had a baffle in it.  The purpose of the baffle was to eliminate oil starvation at the oil pickup screen during very hard braking, especially if going downhill.   The parts are available and are a popular conversion.  Anton Largiader's website has a lot more information on the situation.

   
Breather system:  
The sketches are unclear about the layout of the breather system.  The sketches for THAT are both of the /7 era, so the sketches shows the original round-disc type, but do show, very UNclearly, the oil condensation return hole #22.

The breather system varies from the early models to the later model, but the basics are the same. Engines FROM 1978 had the tiny return bore hole, item 22, being a 1.5 mm bore where breather vapors condense and are returned to the crankcase.  Item 22 is called the "Return Bore in Settling Chamber" whilst the somewhat harder to understand item 21 is the actual settling chamber.  Item 20 is the breather valve.  Shown is the earlier spring loaded (and adjustable to two positions for the smaller versus larger engines) round disc type.  The disc type tends to get chipped edges and also sometimes makes noises.  The original disc can be made up from something like printed circuit board material, if one wanted to.  The later reed type can be installed in earlier disc type engines.  There is really nothing wrong with using the disc type, although they sometimes makes noises.

Further information on the breather system is contained at: oilingsystem.htm

The pressure sensor switch area might have 14.5-29 psi (1-2 Bars) at about 800-1000 rpm, and perhaps 60-74 psi (up to roughly 5 Bars) at 4000+ rpm.   This all varies considerably with temperature of the oil, viscosity of the oil, and condition of the various parts of the engine.  The switch threads are reportedly 12 x 1.5 mm. Early /5 threads were PIPE threads.  NOT so the later threads!!

   

    Note:  A RARE event, but has been seen now and then, is an engine with the front main bearing having rotated, which cuts off oil to the rocker arms, and lowers oil pressure.  You will usually find a steel pin, of about 4 mm diameter, about 11 mm long, in the oil pan.  Whilst the main bearing is a press-fit, if the pin, which is supposed to be pressed-in and staked, comes out (big oil pressure is there, helping to push out the pin), then the bearing MIGHT rotate.  The pin is 11-11-1-253-184.   This is a SERIOUS event, and requires the entire front of the engine to be disassembled.

Revisions:
09/21/2003:  add information on phase in identification numbers and the Alcan mark.
08/24/2004:  add switch thread information
07/05/2005:  Revise for clarity of years and models, etc., the breather information.  
12/21/2006:  Completely revise, with much clearer and very much larger sketch, edit the text for clarity, and add a table for the 25 sketch items.
02/03/2008:  Remove engineinternals.htm hyperlinks.
04/28/2008:  add thermostat information
05/08/2008:  minor clarifications and editing AND add the 1980+ oiling sketch.

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