Hi everyone,
Im a new member here. I just bought a 2001 monte carlo SS 3.8.
I had a new engine put into her, the engine seems to be running great for 90,000 miles but after about ten minutes of driving the "low oil pressure" light comes on and the gauge goes down. it seems to bounce back up if you hit a bump "sometimes!!". The mechanic who put in the engine said he put in a brand new sending unit and also checked over the wiring harness for loose wires, but still nothing. the engine seems to still run smooth but i cant trust it. Any suggestions or similar happenings.

 

The 1st thing & safest thing to do is get a oil pressure gauge or your mechanic should have one & check the oil pressure.
That should give you a true reading on oil pressure & you will know if your pressure is OK or bad. I'm sure you have checked your oil level & it was `OK ?

It could be a clog also in your oil pressure pickup line ?
Check back to see what our tech member's post on this problem...Good Luck!

p.s. What weight oil are you using ? How many miles on your Monte since it's been changed ?

Hi Dan, I just read your Oil Pressure Problem thread & if it changes when you hit a bump (?), it sure sounds like a bad connection on either end ?

 

Welcome! I hope you get your issue figured out soon. Good luck! I had an '03 SS with the 3.8 and loved it!

 

3.8L Engine

• Before servicing the vehicle, refer to the Precautions Section.
• Disconnect battery negative cable from battery and properly isolate to prevent accidental reconnection.
• Disconnect oil pressure sensor electrical connector.
• Remove the oil pressure sensor.
  
  
  
  
  Fig. Location of oil pressure sensor-3.8L engine
  
  

To install:

• Install the oil pressure sensor and tighten to 12 ft. lbs. (16 Nm)
• Connect oil pressure sensor electrical connector.
• Reconnect negative battery cable.

5.7L Engine

• Before servicing the vehicle, refer to the Precautions Section.
• Disconnect battery negative cable from battery and properly isolate to prevent accidental reconnection.
• Remove the intake manifold.
• Disconnect the oil pressure sensor electrical connector.
  WARNING
  Clean the area around the sensor before removal. This avoids debris from entering the engine.
  
  
  
  
  
  
  
  Fig. Location and installation/removal of oil pressure sensor-5.7L engine
  
  

To install:

• If installing the old sensor, apply thread sealant GM P/N 12346004,(Canadian P/N 1093480), or equivalent electrically-conductive sealant.
• Use special tool J 41712 or a suitable socket to install the oil pressure sensor to the engine block and tighten to 15 ft. lbs. (20 Nm)
• Connect the oil pressure sensor electrical connector.
• Install the intake manifold.
• Reconnect negative battery cable.

 

So I went to my friends garage and lift. We find a some what Bare wire that we fixed on the sensor that is on the front side of the oil pan. I went for a ride around and the same problem existed. When I got home I got you reply. The schematic pic you sent me will be helpful because I thought the sensor and the sending unit were one in the same, but now I see they are not. I'm gonna go back up there and check that also. Are you sure that the schematic is for a 3.8, and not a 3.4?

It could be a clog also in your oil pressure pickup line ?
Check back to see what our tech member's post on this problem...Good Luck!

 

I suspect you have an oil pressure sensor that is leaking. You stated it runs fine, shows low oil pressure, plus a leak usually nails the sensor as being bad. It is located on the passenger side toward the rear front (belt side) of the engine. Heres a pic.

.

 

There is no leak any where at all though

 

Hopefully, one of our expert motor head member will chime in & help with your mystery problem...

Did you use a oil pressure gauge to check your oil pressure ? Your mechanic should have one (?) maybe ?
Then you would know if it's a bad sensor/connection or connections to your Monte's gauge if the pressure gauge shows good pressure.