Greetings, SOL's
I have been experiencing strange oil pressure readings in my '68
MGB. They began before I rebuilt the engine in February (providing
some of the impetus to do the work), and have continued since, to a
lesser degree. Since I am planning to drive over the Rockies and take
up residence in Boulder in January, I would like to resolve the
problem here where it's still warm.
Prior to the rebuild the engine had zero pressure at idle, which
would come up to better than 50psi above 3K rpm. This was the case
when I bought the car, and continued for seven years of daily
driving. When the oil pressure began occaisional drastic fluctuations
at speed and a compression check revealed that it was indeed time,
the B went into My Tool Crazy Brother's Garage in San Diego. My
opinion of the oil gauge's accuracy went up when an inspection of the
cam bearings showed that I probably did have zero pressure at idle.
It was good that I trusted the gauge at this point, since firing up
the engine after the rebuild showed no pressure, so I shut it off
after a few seconds. Some sleuthing revealed that the wrong gasket had
been used on the new oil pump, which was a slightly different
configuration from the old.
Ok, so now, after the rebuild, I have 35-55 psi at hot idle, and
50-70 psi above 3k rpm. The fluctuations within these limits are
random, and do not correlate with temperature, rpm, road grade,
precise sump levels, or whether I've wiggled the electrical
connection at the sensor. The time scale for the variations is
anywhere from 3 seconds to an hour. I recently replaced the hose from
the block to the sensor, and the connections are tight. However,
there are assorted small oil leaks (of course). Possibly at the front
of the head gasket, around the pan, maybe timing chain cover, etc.
Less than 1 quart per 1000 miles, certainly. Not enough to account
for any oil pressure fluctuations. All the other electrical gauges
read rock steady, and the connections seem OK so I'm leaning towards
blaming the sensor. Too bad they're $100. I wouldn't worry, except I
hate seeing only 50 psi while cruising at 4300 rpm.
So, any suggestions? Are these electrical gauges notorious, or
could the oil pressure really fluctuate like that?
-----------Jean@spock.usc.edu
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