so i've replaced the motor once after it locked up due to loss of oil pressure. 2 weeks later the same problem with the new motor. Now i'm on my third swap and the shop tells me it isn't reading any pressure. what would cause this on 3 different motors? i wasn't sure if it had an external routing for the oil or an oil cooler or what?? does anyone have any ideas why this would keep happening. it is a 2002 bonny sc. if that helps.

Most odd. Where any parts reused when you did the motor swap? Something like the front timing cover.

That is odd. Where did you get the motors at? Is it possible you got motors that were bad and not in a run condition?

Please put your year and model in your signature to help us understand which motor you are having troubles with.

as far as i know nothing has been reused. this time i even had them change the oil sending unit and they had to replace the the tensioner setup or something cause from the grand prix to the bonneville its different? not sure what the problem is. both motors come out of running cars. asnd its an 02 3800 sc. thwe motor come out of an 00 gp

That really is a puzzling question there are many possibilities of what could be wrong with it locking up. Are all the oil plugs secured? Is the oil filter the right size? was the assembly dirty before you installed it or it could be a bad oil pump or combination of any. The crank could be damaged. many things can get sucked into the pump and get it clogged. The pressure relief valve could be stuck. Is there Leakage between the oil pickup tube and pump if so then that could be your culprit if theres leakage your not going to have pressure make sure its installed properly because if its not or its damaged there will be a complete loss of oil pressure.

I've seen a couple motors that didn't like being transplanted. But nothing to this extreme.

Changing the tensioner shouldn't do anything.

They should have had to change the oil filter adapter and oil pan each time as the GP uses one that heads straight at the body and the 00+ B'ville heads under the pan. And the oil pan is part of the passenger motor mount. The oil pick up tube should also be getting changed at the same time. This might be a potential problem area.

When swapping the soil filter adapter there is a required gasket. Also there is the oil pressure plunger and spring. If something is being done improperly this would cause problems. Although it would be tough to do something wrong in that area. It'* simply a plunger/spring that gets compressed when the filter adapter is put in place with it'* new gasket.

The things to be questioned would be are the oil pick up tube being swapped and is the proper oil filter adapter and gasket being put on properly? the plunger and spring are the same across the 3800 motors.

I feel your pain brother, I went thru 3 before we found this! When you replace a 3800 motor, depending on whether it came out of a Buick, a Pontiac, or a Chevy, the piece that the oil filter connects to is different. It needs to change to fit in the different cradles. Inside that housing is a relief valve that opens when the motor goes to high RPM to bypass oil pressure and returns when it idles back down. What happened to me was the new motors were fine upon installation until the first higher RPM, once that happens the valve does not return and oil pressure drops to zero spinning main #2. We reused that piece on the next two motors, once changed we were wiser and good to go.

thanks hotrod..noone has ever been able to find a problem with anything but that could just be it. especially since my last swap was out of an 05 monte.