2011 ISX loosing oil pressure

[gator55912]

HELLO, I have a 2011 ISX with around 600,000 miles on a major..I haven't had any problem until recently with my oil pressure..I start out fine with pressure at 40-41 but within an hour of driving it starts to drop and continues to drop down so low I get a check engine and stop engine light..I pull over let the oil cool down and I'm good for awhile again but same problem occurs..my oil temp climbs to 230 and stays there and my H2O is at 185..I just put a new oil pump and mains and rods in but the problem still remains..oil thermostat was replaced 6 months ago when they replaced the front cover gasket..any help would be appreciated..thank you.