changing the cranckshaft bearings will increase the oil pressure?

ONLY IF worn crank bearings are the actual mechanical source of the problem. How many miles on engine? Is the oil pump pick-up screen sludged up to the point that when the engines warmed up the flow is restricted , causing reduced flow/pressure?

TOTALLY agree with that answer!!!!!!.. Got to fix one tomorrow.. 'Exact same problem'..... Got the pan off already... Looks like coal tar in there!!!!!!!!!!! When the oil pressure would drop, could cut engine off for just a few seconds, restart and pressure be ok. For a little while!!! Then repeat same thing!!!... Sound familiar?? Now that's what I've got on this one anyway!!

WOW! I'M CURRENTLY DOING RESEARCH ON THIS PROBLEM WITH MY MOM'S 2003 TOYOTA SIENNA 3.0L CE VAN SLUDGE PROBLEM... EVEN THOUGH WE HAVE CHANGED THE OIL EVERY 3K-3500 MILES!!!!!!! I DUG UP SOME INFO YOU MAY FIND DISGUSTING AS I DID AT THIS FIRST WEBSITE: GO TO: http://www.autosafety.org/toyota-deal-here-comes-the-sludge-judge-0 IT'S UNBELIEVABLE!!!!!!! THEY CUT OFF THE DATE AT 2002... BUT FROM HEARING YOUR STORY... IT CONTINUES ON WITH THE SHITTY ENGINE DESIGN THAT BUILDS UP SLUDGE!!!!!!! I TRUSTED TOYOTA BACK IN THE DAY WHEN MY MOM PURCHASED HER 2003 TOYOTA SIENNA WITH JUST OVER 3000 MILES... FROM A TRUSTED DEALER HER IN TUCSON, AZ. NOW AT 92000 MILES... AFTER CHANGING THE TIMING BELT AND VALVE COVER GASKETS... THEY GAVE US PICTURES OF MAJOR SLUDGING!!!!!!! IT CONTINUES TODAY WITH YOUR 2006!!!!!!! THIS IS HIGHWAY ROBBERY!!!!!!! AND WE CANNOT DO A F***ING THING ABOUT IT NOW AS THE CLASS-ACTION LAW SUIT IS WAY OVER! I THINK WE NEED TO BAN TOGETHER AND CREATE ANOTHER ONE FOR NEWER CARS ABOVE THE 2002 CUT-OFF!!!!!!! EH??????? THIS SUCKS!!!!!!! I WILL NEVER RECOMMEND ANOTHER TOYOTA TO ANYONE....... EVER!!!!!!!