J.B. Hebert wrote:
On my way into work today my low oil light came on. Oil pressure was
fine, so I continued on another minute or 2 and the light went
out. A few miles later I noticed that my oil pressure had started to
fall. When it dipped below .5 bar, I shut off the motor and coasted
to the side of the road. The low oil light had not come back on
again. I popped the hood and checked for leaks or any indication of
a problem. I found no leaks, and the oil level was between min and
max on the dipstick. I restarted the car and the oil pressure went
to about 1.2 bar, but would not go higher as RPMs increased. After
10 seconds or so of running it started to drop again so I shut the
motor off again. The vehicle has shown no signs of a failing oil
pump or any other issues. It normally idles around 1.8 to 2 bar and
pegs the needle quickly. There are no odd sounds, smells, or
sights. Now, I changed the oil filter last night (Mann filter, just
like always), which is the only thing I've done to the car
recently. I have no idea if it's coincidence or not, but I plan on
pulling the filter tonight to see if I can see anything wrong. Even
if the filter was faulty and stopped oil flow, there is a filter
bypass so I should not have seen the symptoms I'm seeing. It appears
that the oil is not flowing back down to the sump quickly enough and
the pump is sucking air. I'm having the vehicle towed home for
further diagnosis, but welcome any suggestions.
Check the pressure transducer. Resistance should be a few ohms at NO
pressure (engine not running) and a bit less than 200 ohms at 3 bar. If
the oil pump were to fail, that could do it (but that's VERY rare unless
the pump has ingested some metal debris - say from a disintegrating
vacuum pump - that jams it) or if the overpressure valve in the oil
filter housing or the one near the oil pump jam open.
Oil pressure transducer failures (they sometimes open and sometimes
short) are FAR, FAR more common.
http://mb.braingears.com/124_DISC2/Program/Chassis/54-0254.pdf
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 182Kmi, '85 190D 2.0 161Kmi, '87 190D 2.5 turbo 237kmi, '84
190D 2.2 229Kmi (retired)
