Oil pressure drop
At engine startup on my '40 Ford with stock engine, my oil pressure gauge reads 45+ lbs of pressure on the factory gauge and has done this for quite a few years. After driving for 20-30 minutes and the oil is up to temperature the gauge reads around 10 lbs going down the road and maybe 5 lbs. at idle. My oil pressure sending unit is an old one; maybe the original.
My questions are:
- Is the sending unit malfunctioning perhaps due to age?
- Is it possibly a weak pressure relief spring playing tricks when the oil gets hot?
- Is it a faulty gauge? (it's old too)
...or a combination of the above?
I want to make sure I am diagnosing my problem before I order and replace a part unnecessarily.
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