Deep oil pans

BMW motorcycle deep oil pan

By Duane Ausherman

This page is about the deep oil pan for the /2, but most of it applies to the /5 and later bikes.  Several types of accessory oil pan products have been offered.  I think that I have seen, or heard about, at least six types of the accessory pan for the BMW motorcycle.

One had deeper fins for more cooling and was cast out of aluminum.  The idea was to improve the cooling of the existing quantity of oil, not increase the air volume.

Another type was a spacer.  It used the stock oil pan as the bottom.  It “sandwiched” a cast aluminum spacer in between the block and the stock pan.  It also used a spacer to lower the pickup.  The bolts that hold it on can come loose and fall into the pan.  It was supposed to have a sheet metal retainer that could be folded up against the bolts to keep them in place.  It required two gaskets on the pan and two gaskets on the oil pick-up.  This one held more oil but didn’t increase the cooling significantly.  Since it didn’t come with a longer dipstick, one just kept the same level.

At least one pan had a few air tubes running lengthwise through it for air to flow through.  It held more oil and cooled it a bit better.

One pan is reported to have the oil drain in the front.  Another one seems not to have spring mounts for the stand.  Another one was reported to be of very low quality.

The two possible reasons for using a deep sump are both “slightly” valid.  On the /2 and /5, they were to help cool a “perceived” hot engine.  In very few cases, it may have been necessary, some of which it was the wrong way to cool. That is another story.  While the /2 suffered some piston overheating, the oil was never an issue in solo riding.  In the afternoon, I have ridden the R60/2 (certainly the worst one for heat) across Death Valley in the middle of August.  The only thermometer I saw said it was 125 F. I believe it.  Yes, I was stupid.  Neither the bike nor I had trouble with overheating.

With the advent of the 900 cc engine and the resulting leaks and noises, some figured that the easy way to increase the air volume was to drop the oil level.  After all, a piston engine is almost the same thing as an air compressor.  That is quite smart.  That drops the peak air pressure that is caused by the large 900 cc pistons coming to BDC.  The high pressure causes the oil to go past the seal and generally leak from other places too.  It reduces the negative peak pressure caused by the pistons going to TDC.  Any air escaping or being pulled past the seal can make some odd noises.  Air gets sucked into the engine crankcase and is the real problem.  This greater amount of air gets compressed to a higher peak, and the official breather can’t handle it.  The solution was to develop a rear main seal that didn’t allow air to get sucked into the crankcase.

Some riders add an oil temperature gauge to the motorcycle.  More than one accessory pan had a provision for a temp sensor.  That is fine if you are the type of person that wants instrumentation.  It is for looks, but it isn’t for any need.  You have only added another place for oil to leak and cause trouble for normal maintenance.  These bikes don’t get the oil hot under any normal conditions.  Relax and ride.

In conclusion, Don’t waste your money.

Stripped pan bolts

The pan bolts are easily stripped out of the threads in the crankcase.  It is easy to think that they must be tight so that they don’t fall out.  One might fall out.  That would be bad, as the oil would run out quickly.  I have never seen this happen.  What happens is that owners overtighten the bolts, strip out the threads, and don’t know.  Then it leaks.  The bolts only need to be tightened up a very small amount.  There is a variety of types of gasket material available.  The /2 used a cork gasket.  That one was a bit difficult because the gasket would shrink and leak.  It needed to be tightened up soon after use.  That pan is made of sheet metal and would easily warp.  Over tightening easily warps it, and then it leaks.  Use your favorite sealer on the gasket and bolts.  Oil can run down the threads of the bolts.  Then gently tighten up the bolts.  Then check them often at first.

I understand that silicone gaskets are now available, and they seal well.

One choice of a pan for the /2. Photo from Jim, thanks

One email I received.

Hi Duane, I got the new pan from S.  Meyer in Germany and cost 78 Euro plus 29 Euro Postage to Australia.  It has the pickup extension and the lug for the side stand spring, although it is not drilled.  It has a row of small cooling fins along the bottom, has a drain hole at the rear, and comes with stainless cap screws to mount it.  I am not sure of the volume.  I THINK it is 2.5 Liters.  With the pickup extension installed, the screen is only a couple of mm above the pan’s bottom.  It is very nicely made and almost matches the crankcase in color and texture.

Stephan Robinson

Updated 15 July 2022