Hi,

I have a Trailblazer 2001, 4.3 V6. Some time ago the oil pressure started to go to about 20, or even a bit lower while standing at red light. As soon as RPM are over 2000, oil pressure is at 40. Also the oil pressure only goes lower when the motor is warm, freshly started it always stays at 40, independent of RPM.
I read through the forum, which already helped me a lot in the past, and I started to change the oil pressure sensor unit, which seems to be the cause for porblems like this in most of the cases, However, changing the unit didn't solve the problem.
What do you guys think what I should do next? Replace the oil pump?

Thank you!
Best
Valentin

 

Engine service manual describes MINIMUM oil pressures:
- 6 PSI for 1k rpm
- 18PSI for 2k rpm
- 24PSI for 4k rpm
A warmed oil of 80 centigrades definitely has less viscosity than a cold one, so an oil pressure drop isn't anything unusual.
An oil pump is transferring the oil through the engine galleys and crank/cam shafts bearings. The more worn off the bearings are, the easier for the oil to flow through. 20PSI or below on idle, apart of the oil pump may indicate a worn off engine bearings.

What's your mileage?

Replacing the oil pump requires an oil pan disassembly, which - as far as I know - requires hoisting the engine due to a cross bar under the engine. Crankshaft engine bearings and connecting rod bearings can be measured from underneath the oil pan. Yet, You have to prepare a complete TTY bolt set - You can't use same bolt twice.
If You decide to replace the cam bearings, You more likely are going to overhaul all the engine... Sometimes it's wiser to look another, spare engine and save Yourself a job.
Brgds, Mike

 

Hey Mike, thanks for your answer.
Mileage: 115k, but I guess, regarding your answer I will leave everything as it is right now as long as the pressure doesn't drop any further
You helped me a lot,
Have a nice sunday
best
Valentin

 

Your oil pressure is fine, completely normal readings