Oil Pressure Problems

Posted by Jim L. in OR On 2012/7/2 18:21:03

Hi people,
Since I got my '55 Patrician (AKA Sleeping Beauty) back 2 weeks ago I have confined my driving to surface streets and other non-freeway routes while the car and I got acquainted. During that time, everything under the hood exceeded expectations.
This last Saturday I took her out on the freeway for the first time. As I was merging from the on-ramp another car that was going quite fast ignored my turn signal and came into my lane. I was at a merge or stop situation so I punched the accelerator which resulted in a perfect downshift and a dramatic increase in speed leaving the offending driver in the dust. I also got a brief wiff of hot oil smell. I was headed to the grocery store which was a mile down the freeway and concerned about the smell of hot oil, check the pressure gauge. It was showing about 20 psi instead of 40 at about 55mph and by the time I pulled into the first available parking place the pressure gauge read zero. Aside from the oil pressure there was no indication of trouble - no lifter clatter or knocking - just a quiet smooth idle. I had quite a shopping list so I decided to do that, load the groceries in the trunk and call a tow truck. The shopping took 30-45 minutes and before calling AAA, I decided to start the engine and see what happened. The engine sprang into life, as quiet as the tomb and the oil pressure gauge read perfect pressure so I slowly drove home. By the time I got into the driveway the pressure was back to zero at idle, with about 20 psi the last few blocks to my house.

I checked the gauge and it was fine so I pulled the sending unit and put a manual hook up in it's place. Upon restart, the pressure was fine. Having had enough excitement, I postponed any further testing until the next day.

Sunday morning I repeated my freeway trip of the day before with the exact some results using the manual gauge.

Today I made the same trip using surface streets and a top speed of 35 mph and had no oil pressure issues.

My chief suspect at this point is the oil pressure relieve valve. The car doesn't have the infamous Packard oil pump. That was changed out sometime in the past with an unknown replacement.

The amazing thing to me is that through it all, the engine is as quiet, smooth and responsive as it can be. It almost seems as if there isn't really any problem - but two oil pressure gauges say there is.

Does anyone have any ideas and or solutions they've used?

Thanks in advance -