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Images reveal a lot of contamination. Be sure to completely disassemble the Oil Temperature Regulator and clean. You might be amazed with what, and how much, resides there. And anywhere oil flows; especially up to and from the injection pump, clean with brush and solvent.

 

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"Disassemble 'oil temp regulator'...do you mean oil cooler temp bypass?"

Yes, per the diagram.

If the "missing" tank screen parts went through to the oiling pressure pump there will be visible damage to both of the gears and, very possibly the housing. And if the debris made their way to the engine sump, you'll see similar damage to the scavenge pump components and the housing.