I wouldn't use flushing oil though - I drain the old & refill with a cheap (really cheap) oil and go for a 30 min ish drive.
Drain it off when you get back - you'll be amazed the difference in colour compared to when you put it in........
I don't even know if the part-blockage thing is possible really, just a thought!!
Not sure about testing the sender units - maybe something in the archives.
well i've stuck the relief valve back in no probs.
checked the pressure sender and all seems ok, discoonect one connector and you lose the oil pressure light, disconnect the other and the gauge goes full scale when engine not running.
all as expected.
However, gauge always reads one full yellow bar even when only ignition on and engine not running. Given that the gauge is therefore overreading by this, maybe the pressure does drop when the oil is warm but it doesnt show on the gauge as it is still overeading and showing full.
if it wasnt overeading in the first place then maybe it would show a drop in pressure when warm.
Does anyone know how much the sensor is and how to chanage it??