New member with low oil pressure problem

[Bob_Roller]

My '81, the original tube from what I remember was about 2 inches long .

I installed an oil cooler kit and there was a new tube that went all the way to the filter cover  .

[Barry]

I've never measured it but on my 79 I'd say the pipe is a little less than 2"  it's Just long enough to locate the filter on.

The oil flows from the main filter tube through the filter from the outside to the inside and out of that pipe into the oil galleries.

I supposed at first that if there was blockage in that pipe it could reduce oil pressure but on reflection it wouldn't as the oil would just see it as a blocked filter and go through the bypass valve instead.

Have you seen the attached description and diagram of how the lubrication system works. I've added the diagram as a separate image as it's much higher quality allowing you to zoom in and really see the detail.

[mrclubike]

The symptoms you describe sure sounds like a faulty oil pressure switch
I am not sure but doesn't the switch out of a Volkswagen fit it or something like that.
What part of Mo are you in.
I would think Engels in KC or Gateway in St Louis would have the switch in stock  

[montmil]

Two items to be aware of, if considering utilizing the Volkswagen OP sender switch:

1. Threads on some of the switches do not match the BMW crankcase threads.
2. Confirm that VW's OP switch activation pressure matches that req'd for the Airhead.

No concerns with using OEM switch.

[thrang]

Assuming that you installed the filter correctly, have the right oil volume in the bike and have no obvious oil leaks, then its most likely to be the wiring to the switch or the pressure switch its self at fault. A new pressure switch is only about £10 from Motorworks.

[minitoo]

Just a thought and simple things first but what weight oil did you put in it?

[JJH]

I could not find the correct OP switch at the local auto parts store.  The VW ones had smaller threads M10 X 1.0 not the M12 X 1.5   No one had the oil switch for the BMW 2002 in stock.  On another note, I bought a cheap oil filter tester from Harbor Freight.  I carefully removed and very carefully screwed in the tester.  I barely snugged up the tester.  I started the bike and at idle it rad 90 psi and when revved it was over 140 psi.  Now Harbor Freight only sells the cheapest and low quality tools available anywhere in the world, so I wasn't too surprised by the values.  But one thing to note the oil was pumping at a great rate from the tester.  I tightened it up a bit, but it still leaked from the oil pressure switch hole.  What this indicates to me is there is more than 3-5 psi being generated (I think that is the cut off for lighting the oil pressure switch).  I removed the tester and placed the oil pressure switch back in.  I started the bike and after ~15 seconds the oil pressure light came on, when I revved the engine it went off, when back at idle it came back on weakly.

I am travelling to the city for holiday tomorrow, and will be stopping off at the dealership to pick up an oil pan gasket and a new oil pressure switch.  Is there anything else to pick up to help me trouble shoot this problem?

Thanks,
John

[Luca]

From what you describe it sure does sound like it's just a faulty switch.  Your HF tool might be cheap, but it's not going to be off by 80+ psi.

Before you worry any more about it, I'd just put the new switch in and see how it behaves.

Also, I assume your GEN light is regularly coming on at idle as well?  I can't recall if they have the same bulb, but maybe it's possible that the GEN light and OIL light got swapped if you're not seeing the GEN light

[JJH]

That is what I am starting to think.  It is definitely the oil light.  The gen light comes on at idle and fades at higher rpms as it should do.
Thanks,

[montmil]

Confirm dash lights are in their correct bulb holder by checking the wiring diagram for wire color-codes.

[Barry]

Well whatever it is you must be mightily pleased it's not a major problem after the oil pressure test.  The original switch spec. is 0.2 - 0.5 bar or approx. 3 - 7 psi.  Seems to me the damage is done at 3 psi and if I was looking for switch within reason I'd pick the highest pressure  I could find.

Here's an oil pressure switch catalogue that might give you some part numbers to search for.

[Bob_Roller]

Don't be surprised by the oil pressure you saw on the test indicator, these bikes have lots of oil pressure .

It doesn't happen too often, but owners of airhead BMW bikes have found collapsed oil filters when they change them .

Go easy on the throttle in cold temps, pressure can easily exceed 150 psi on first cold start up .

[mrclubike]

Remember 20W50 is darn thick oil when it is cold
To really know what is happening you need to check the pressure after it is fully warm.
That pressure will come down when the oil gets up to operating temp.
I really think you just have a faulty pressure switch.
Put a new oil pressure switch in it and see what happens.

[JJH]

Well I installed a new oil pressure switch and took the bike out for a few runs and no oil pressure light.  So I guess it was a faulty sensor.  Thanks for all the help that you provided.  
John