Assuming you mean oil pressure, check all the fluid levels NOW. You may be low on oil.
I may not be understanding your question. Of course the oil pressure goes to 0 when you shut the engine off, as the oil pump is no longer runnning. Start the engine and the pump brings the pressure back up. I don't know what you mean by, "bleed down".
goes down
mean arterial pressure
Pressure of the defender
goes down
If you mean the light it should reset itself while driving
Your tachometer is broken.
wire came off of the sensor (for oil pressure) or the sensor is bad. Or your oil pump is not working (not likely if you have been driving it at all). My 99 did not show pressure for a few minutes or would bounce up and down. Repalced and problem went away
It means that the pressure pushing you up is greater than the pressure pulling you down.
low tire pressure
its for traction