Chrysler Repair: Oil Pressure Problem, pressure relief valve, accurate gauge

Question
Hello Roland.  Thanks for your time in advance.  I have a 91 5th ave 3.3L (R) with 200k miles.  Oil has been changed reliably every 2500 miles or less.  Problem is, when the engine warms, the oil pressure drops.  Especially at idle.  The oil pressure sensor has been replaced.  My question is, is there any way to tell what the cause is.  The oil pump has never been replaced as well as the pressure relief valve that is located in the block below the timing cover.  Is ther any way to diagnose weather it is the pressure relief valve, the oil pump(which im sure you know, but is a big job), or the lower berings?  

Thanks again,
Chris


Answer
Hi Chris,
Does it drop below 5 psi at idle as measured with an accurate gauge, and 30 psi at 3,000 rpm? If not then I wouldn't worry. I don't know of how to differentially diagnose the pump from the relief valve or the bearings. But I would try the least costly repair first. Another approach, if the actual pressure comes close to meeting specs, would be to increase the 'weight' of your oil by one step if you want to get the light to go 'off' and meet specs at the same time.
Roland
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