Re: Flickering Oil Light

[BOBINYELM@xxxxxxx]

You didn't state the engine mileage, but it sounds like a worn engine to me. 
At idle hot, the pump is not able to make enough volume to make enough 
pressure (about 7 psi or 0.5 atm) due to the volume of hot thin oil escaping 
past worn bearings.

There are other things that will cause this:

1) Worn oil pump (unlikely since these things are constantly bathed in oil, 
clean oil I hope).

2) Stuck oil pressure relief valve. I had this problem with my 3.5 liter e23 
B9 Alpina. The former owner used a brand of oil that varnished the inside of 
the block a bit, and through non-use, left enough deposits that the relief 
check valve wasn't closing all the way, allowing oil to bypass back to the 
sump. I solven cleaned the pump and relief valve and the problem went away, 
with the idle pressure a decent 1.0 atm reading.

3) Bad oil pressure switch.

First thing is to attach an accurate mechanical gauge to the oil pressure 
sender port and check the actual pressure. If it is more than 0.5 atm at idle 
with the engine at full operating temperature (and the engine run enough to 
elevate the oil temp to its max value), then it's a sending unit problem If 
it is below 0.5 atm, then it is one of the above problems.

You might try a different brand/grade of oil as well. Possibly what you are 
using is losing viscosity at operating temperature, though it is unlikely 
that this alone could be your problem.

If it is a pressure problem, when you remove the oil pump to check the relief 
valve, you might consider replacing the big end (connecting rod) bearings. 
They wear the most, especially if the engine was ever lugged. I replaced a 
set that was worn to the copper backing on a 2.7 eta engine at only 100K that 
was otherwise an unworn engine. I forget the model you have, but on most 
models you can pull the oil pan and do the mentioned work with the engine in 
situ.

Bob

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