My oil pressure is becoming unstable, most likely it is because of the O-rings on the center stem in the oil filter housing. I can't find them anywhere by description. Does anyone know the dimensions of those O-rings? they appear to be different sizes.

 

Thanks, the sensor might also explain why the gauge goes to full pressure with the key on engine off. I thought that was a hydraulic gauge all of this time. thought I was loosing my mind.
I have another question. I called my local parts store to purchase a water pump, they tell me that I will also need some kind of drain line. Is this true, or are they trying to sell extra parts?

 

Thanks I'll look elsewhere for my parts.