I have a 720D that when cold the oil pressure pegs to the high point on the gage , and as it warms up , the oil pressure runs just at L at fast idle, and below L at normal idle. I am using 10/30 rotella oil.
Someone said it could be the spring in the oil relief valve is bad, so bought another relief valve on ebay since you can't get these springs anymore.
When I look at the two springs, what a difference in size. My original spring looks twice as long as the one I bought. It looks like someone stretched my spring out for some reason. Maybe trying to get a higher pressure?
Anyway , I changed the oil to standard 30 weight Rodilla diesel oil. Also I changed the relief valve and spring to one I bought on the ebay.. Both of these seemed to have no real affect on the pressure. Except now, the pressure is at L all the time and not at H when cold. When warm, it hovers below L.
I am now wondering if my gage could be bad. Can someone recommend a good quality oil gage that has numbers on it rather L M H , so I can see the actual pressure. Also I am going to change the oil to a standard 40 wt. Any other suggestions would be helpful.
If this doesn't work, I assume that the main bearings are bad. Can these bearings be changed without removing the crank, and would this help?