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oil pressure low

Shav0

By Shav0
in Ask A GM Technician

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Shav0 Enthusiast

Shav0

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89 GMC Sierra 1/2 ton, 350.

When the engines cold, my oil pressure is somwhere around 60 psi, however, as the temp comes up to operating temp I loose my oil pressure as low as 30 PSI, and even lower when im at a idle. Is this normal or should I be investigating more?

thecraft Senior Enthusiast

thecraft

Posted
Posted

That seems normal, when mine is warm and idling, it is just over 20psi. When it gets lower than that, then it's time to panic.

  • 3 weeks later...
Shav0 Enthusiast

Shav0

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Update:

 

My oil pressure is still droping. When i first got the truck it would stay at about 275 kpa (40 psi) regardless of temp or engine speed. I've noticed it droping further and further all the time. It only had 158xxx kms on it when I bought it, and i've only put 5000 km's on it and now my idle oil pressure is somwhere around 100 kpa (14 psi) and will only increase to about 25 psi at highway speed (1700 rpm's). My idle engine speed is only about 600 rpm, yet a few short months ago my oil pressure was much higher. Shouldn't it increase more when im driving then only 10 psi? I have a friend who has the same truck, same year and his runs 50 psi all the time, regardless of engine speed. Im starting to get a little worried that somthing must be going on. I know the spec is only about 6 psi, but something seems werid that it keeps droping lower and lower all the time...

 

Where should I start first? My engine runs great, no noises or knocks, so I don't think it's anything internal like bearings or anything getting worn, however would it be worth the 100 bucks to throw a new oil pump in it? Perhaps the pressure relief valve is getting lazy and opening to soon? I'd like to see it back up to the 40 psi that I started out with or higher.

 

Where is the location of the pressure sensor on the 350? And is there a place where I can hook up a manual gauge just to make sure?

tim73 Enthusiast

tim73

Posted
Posted

Id definitely check it with a manual pressure gauge, before I would worry about it. May just be a bad sending unit/and or gauge.

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