hi fellow blazer people,here goes,i have a 2000 s-10 blazer-4x4,4.3cyl.fuel inj. anyway,had the intake gasket done afew days later comming off the highway oil pressure drops to10lbs,check gauges light comes on.of course i pulled into a gas station to see whats the matter.long story short here i am 40,000 or 50,000 miles laterit still runs like atop but oil pressure drops from60lbs to10-15lbs after warming up,i also get this rapping noise when shifting from 1st to 2nd gear,its an automatic tranny so rpms range would be between 1500 to2000,any ideas i would greatly appreciate i really want to keep this truck.can anyone tell me or point me in the direction to repair my favorite vehicle thanx in advance,sorry so long of a thread or post

 

Could be a rod bearing or main bearing.

 

Any noise when you start from the lower end when you first start or just when you are at higher RPMs.
Any way sounds like Diaita said, I would lean more to rod bearings if your not adding oil.
Depends on how in love you are with it as to how far you go.

You could drain the oil and look for metal and go from there or add a can of STP. If that holds the pressure pretty good sign to fix you will need to crack the motor open. Or sell it.

 

aiight. first off. the oil sender units for theses suck.


All you can do right now is install a mechanical oil gauge (to rule out any sensors electrical bs). if its low,THEN you have a problem. if fine replace the sensor. no point is changing the oil pump. it doesnt give your any oil pressure. its the clearances in there bearings etc.

Honestly if its not the sender unit. time for a engine.


these 4.3s only need 6psi for every 1k rpm.

 

Could be a weak spring in the bypass valve, (regulating valve) located at the oil filter adapter, left rear of block where the cooler lines attach:



Less than $20 in parts, (valve & gasket set) and about 1 hour labor. When the spring weakens or breaks, oil pressure drops like a rock, especially at low RPM.

EDIT: May have a piece of crud, (from the intake job) stuck in there holding the check ball open too. If the ball sticks shut, it'll blow the oil filter clean off... thud, big mess!

 

my fullsize did this. it would start at like 45 then go down to 10psi after it was warmed up, never knocked or anything. i put some lucas in it and now the lowest it goes is 20. probably just cleaned out some crap on the sensor.... or clogged it up even more