Oil pressure, oil pump, pressure sensor, 1990 200

["Brinkmann, Gerardo V" <brinkg@uf4124p01.BheightsNJ.ncr.com>]

>Can this be just a faulty oil pressure
>sensor? If that was the case then how
>could the problem vanish with an oil
>change?

It is not unusually for oil pressure to "improve" after an oil change.
Sometimes gunk forms on the oil pressure sender,
which gets removed after new, clean oil has circulated through the system.
Also the fresh oil will have a more stable
viscosity than the old oil and this shows up as an improvement in oil
pressure.


> Any ideas on how to check and hunt the
> source down of this problem short of pulling
> the oil pump and redoing oil filters and
> everything else related to the lube system?

First you have to be absolutely certain that you do in fact have an oil
pressure problem. Buy a mechanical
oil pressure gauge and hook it up directly to the engine. Read the various
pressures with engine cold, hot, very hot.
Look up the specs in the Bentley manual for what the pressure should read at
various RPMs. If the pressures are within
spec, then the problem lies with the oil pressure sender(s), with the wiring
or with the oil control unit (4000Q).
 
If you do have a pressure problem it could be one of several factors (noe of
which are cheap to fix) :
1 - bad/dying oil pump
2 - rod bearing with too much clearance
3 - main bearings with too much clearance