190E 2.6 0 Oil pressure when idling at 600 rpm and hot

I acquired a super clean great running 190E 2.6 last year with 123k miles on it. Oil pressure goes full scale when cold and above 1100 rpm when hot. At
idle, in gear when hot, the oilpressure sometimes goes all the way down to 0 and sometimes to about .4 on the scale. I understand from the manual that Oil pressure at idle of .4 is normal when hot and at idle and is no problem as long as it goes back up when the rpm's are increased. The previous owner told me that it had always done that and that this is not a problem. When I was digging through the paperwork that came with the car I found a recent receipt for replacement of the oil pressure sender. Could it be something else like a bypass valve that might stick open? Any comment, ideas would be appreciated. Pete
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Does your engine make a clatter when the pressure goes to 0?? If not, it is maybe not accurate.

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Check the viscosity of the oil. 15W40 is a great all season oil. Look in the oil fill hole with the engine running and see if you can see the oil being sprayed on the cam lobes. If you have good flow, hook up a manual oil pressure gauge to the oil pressure sender port and check actual pressure cold and hot. The other thing to look for is the cam oiler pipe under the valve cover. The rearmost 10mm bolt likes to loosen up with time. If the oiler is too loose, you will lose oil pressure. We loctite the bolt whenever we have to pop the valve cover.
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Thank you very much for the info. Pete

being sprayed on the cam lobes. If you have good flow, hook up a manual oil pressure gauge to the oil pressure sender port and check actual pressure cold and hot. The other thing to look for is the cam oiler pipe under the valve cover. The rearmost 10mm bolt likes to loosen up with time. If the oiler is too loose, you will lose oil pressure. We loctite the bolt whenever we have to pop the valve cover.

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