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916 Low Oil Pressure, Not Sensor Issue?

Discussion in 'Technical Help' started by jared, Mar 26, 2017.

  1. HI,

    (first post so hopefully i can get what you need, and post it correctly)

    Having bought, what i thought, was a bargain 916 on eBay, i got a bit of a duffer...

    Turns out price was reflective of oil galley plug backing out and starting to rub on main bearing. Aluminium pieces in oil strainer was the clue. Having restored a number of bikes (slowly) over the years i though i would give this one a go.... TBH it was all fairly easy and a great enjoyment.

    So stripped engine down, split cases, replaced galley with steel version, and built this all back up. Doing end float, checked crank clearance and adjusted all the valve clearances, new belts, ground valves etc.

    Problem, is i still have low pressure at idle once engine has warmed up fully (180 deg F). First test to road of resolution, was actual pressure reading, which did come up low at idle 1.0 bar/14 psi. slight rev increase and the light goes out, so sensor seems okay.

    Started with easy to do and cheapest options...Drained oil and replaced with 10W50, changed oil filter, checked oil cooler pipes, cleaned oil pickup gauze.

    I then moved onto ensure the oil pump was all within tolerance, which it is. Made sure the o ring between right case and oil feed was in place, have checked the relief valve (when engine was being reassembled) and this move freely, so unlikely to be stuck open (but could be). From engine build the Crank to bearing clearance was 0.038mm so well within spec. Small end was fine but does not have oil flow, so discounted this.

    Question is what to look for next? Reading seems to indicate possible camshaft to journal wear (or haynes book states this) correct me if i am wrong but cam shafts are in needle type bearings so i can't see how there is a clearance here, let alone one that allows resistance to oil.

    I have noticed that there is a recommended clearance of 0.03-0.06 with SL of 0.08mm between rocker-arm to shaft clearance. Could this be the cause? and how is this measured? All measurements in this area i have been focused on the valve clearances, but was unaware at the time of checking this. (i am not a mechanic, but am quite handy with spanner and technical instruction. but there was no instruction to check this)

    Any help/advice that you ppl on here can give will be greatly appreciated.

    Thank-you.
     
  2. Are you sure that shouldn't read crankshaft to journal wear??
     
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  3. Hi Old Rider,

    Yes you are correct that it should be crankshaft... It has been a long day!! and a rather long post!!
     
  4. Well I think you'll find that means big ends and oi pressure is a tad crucial there...
     
  5. Ah sorry, i see what you meant now. I thought you were refering to 'crank to journal' not camshaft to journal. The big ends, or crankshaft to journal i checked with plasiguage, and its 0.038mm with a 0.025-0.059 tolerance.

    Back of Haynes for fault finding, says to check:

    Oil pump, pick up guaze, relief valve, oil level, oil viscosity.

    Then possible cause of Camshaft or journals worn. RE-reading i guess it is referring to 2 separate causes for this. either camshafts or journals (big end?), but this is unclear as the resolution is to replace camshaft ot cylinder head, suggesting the journals are in cylinder head, but this does not make sense as there is no journals for the camshafts.. as the next step to check would be Crankshaft and/or Journal wear, but as i know this is in spec i am looking for another possible cause.

    There is a tolerance stated for camshaft to rocker arm, which is likely what i will check next, but unsure as to where this is measured.
     
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  6. Hi Steve,

    Thanks for the input. If this bush was leaking or losing pressure, would it show as oil in the clutch housing? I take you are referring to the bush between clutch basket and crankshaft? i replaced the o ring that fits inside this...

    There is an o-ring on back of engine cover, that is new and in place..
     
  7. Hi
    How many 'miles' has the engine done out of interest ?
     
  8. Are you certain it's not the sensor? I don't know what the oil preasure should be at idle but 14 psi doesn't sound bad to me.
    I would try a new sensor.
    Steve
     
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  9. Just found this on another site, it indicates the oil light goes out well below 14 psi ( 1 bar)
    Steve


    A wee question. I have a 2000 996BP which has a leaking oil pressure switch. Nothing unusual from reading up at MS.
    However, my local dealer sent a new (Genuine) switch which is stamped 0.15 - 0.4 bar. The original is stamped 0.4 - 0.7 bar.
    Should I fit the new switch?
     
  10. Hi,

    Engine has covered 19200 miles, so not a great deal, and has been serviced regularly...
     
    • Thanks Thanks x 1
  11. Looks like I will swap the sensor. Only discounted it as general view on sites that should be 1.1 bar or 15 psi minimum at idle.

    The sensors are known to be problematic, and mine does have oil in the sensor, not leaking but its in there...

    Will order on tomorrow and let you know the out come.

    Thanks for the inputs.
     
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  12. FWIW, the factory manual for my 02 748 specifies the following
    Maximum pressure must never exceed 6 bar.
    Oil pressure values:
    ● Cold engine:
    1100-1300 rpm over 2.5 bar
    3500-4000 rpm between 4 and 6 bar.
    ● Hot engine :
    1100-1300 rpm over 1.1 bar
    3500-4000 rpm between 4 and 6 bar.

    it goes on to say
    "too low a pressure may indicate that relief valve has jammed in the open position or that spring is too soft or pump faulty. Problems with pressure may also arise from worn seals or engine. "

    Did you triple check you got all the aluminium swarf out of it?
     
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  13. The seal Mr R is referring to is item 9 in this drawing from the parts list. The oil travels from oil pump into the clutch cover, the oilway is sealed at the joint by an o-ring ( item 12), then down the centre of the crank to the big ends. The end of the crank fits into the bush 8. The seal should be replaced every time the engine is stripped as it is essential for oil pressure.
    Screen Shot 2017-03-28 at 09.40.49.png
     
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  14. Hi Derek, Many thanks for your detail. Yes this seal was replaced when the engine was stripped. I have ordered a new pressure sensor switch but the figures I was getting are below those posted above so I still think I have an issue..

    I will check the cam shafts over the weekend to make sure they are not worn, from memory they were in good shape otherwise would have been swapped at the time of rebuild.

    Many thanks again.
     

  15. Hi, I am going to pull the left hand cover and check the oil relief valve again. The sensor may be gone (new one on way) but the actual pressure is still low so need to solve that. This will be the last thing that is on the easy list to check fix, before splitting the cases to check the big end a second time (not sure of the need here as I have already don't this during the rebuild)

    |Another option is to get a Ducati mechanic to look at it but the cost alone may mean a second hand engine may be a better option, but that is a step into the unknown and may be back where I am now.

    Thanks for the inputs.
     
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  16. Does the pressure rise steadily and in a linear relation to rpm?.

    Unlikely to be the relief valve but you could shim the spring out for testing, it's main purpose is to limit cold oil pressure and high rpm oil pressure.
     
  17. I would have been tempted to replace the oil cooler as well if you were that far into the job.
     
  18. Main bearing problems are with newer motors then, Steve?
    Are you convinced the pressure actually is low, rather than just reading low?
     
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  19. Not for the pressure but for the chance of having metalic debris inside it..
     
  20. HI,

    Thanks for all the posts and helpful info on this thread. Oil pressure reading is confirmed as definitely low 0.9 once want at idle. I did replace the oil pressure switch, but the new one has a lower threshold than the old so does not kick in until below 0.6 Bar. So the light has went out but still have an issue.

    I did pull the inspection covers off on the head to have a look at the lobes after engine had ran for a few mins, and there was little to no oil in there. Certainly would not ant to run engine under load or for a long period of time.

    So net steps is to trace the oil feed back to the cooler and then the filters to see if oil is indeed feeding to the cams. I would imagine that the is direct result of the low oil pressure, as in not enough to feed to the top end of engine. But still no help to finding the issue.

    Things checked:

    Oil sensor, replaced
    Oil Filter tightness
    Oil pump, checked and replaced and checked again. all clearances are in spec. Gear meshing clearance is very variable on measurement, depending where you put feeler, but did get drag at 0.10mm on teeth..
    O ring in clutch cover oil galley
    Oil seal on end of crankshaft
    Oil relief valve (on alternator side)

    Next things to check:
    Oil feed pipes to head
    Oil cooler for air lock??
    Cam shaft cap orientation, ensure all oil holes are aligned (are I did this on assembly, but looking for everything))
    Final step will be to go back to big end clearances (was measured at 0.038mm on assembly, so well within 0.025mm-0.059mm)

    Some final thoughts Q's
    Would the valve clearances play any part in this? all are 0.17-0.18 intake and 0.22 open/0.12 closing on exhaust.
    When the crank cases were split I replaced all bearings (roller ones in cases) and seals. So fairly sure the issue is not here.
    On the cam shafts the bearings are needle type so I am struggling to see how enough pressure builds to get oil into and through the shafts to the lobes.

    Attached image is from the horizontal Cylinder, looks very clear of oil to me, I know oil ducati cams.JPG drains back but this is as clean as when I put the engine together..


    Will let you know what I find from this.

    Thanks again.
     
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