Low Oil Pressure 78 C10

[Dave W]

Hello,
I have a 1978 2wd  C10 (V8-305) 130k miles (runs good)
After I drive it and it warms up, sitting in drive at a light the oil pressure
starts dipping down pretty low.
It has the original gauge , and reads around 15 when cold,
When it starts dipping the needle gets close to 0, it will
Go up a little of I rev it in neutral
I tried  a little thicker oil (sae30 & 20w50) still the same.
Should I change the oil pump? Also if so can I perform this
With engine in the truck, and are there any brand recommendations
To try and keep this to doing it once?
Thank You in advance!!!

[Irish_Alley]

before doing any of that i would try to get a reading with an aftermarket gauge just to insure the old gauge is still reading right

[bd]

Before doing any repairs verify the oil pressure using a manual test gauge made for that purpose.  Like Irish stated, the real issue may be a faulty sender or gauge. 

To answer some of your questions, the oil pump can be replaced with the engine in the vehicle.  However, low oil pressure can result from various causes other than a worn out oil pump - worn bearings being at the top of that list.

[JohnnyPopper]

Irish and BD have you on the right track.

It's normal for the pressure to drop once warmed up.

Do you hear rods knocking when at operating temp/idle? It's a deeper sound no one likes to hear...

If you don't, it's likely the sender/guage.

If you have to replace the pump, be aware that a stock replacement may not change your situation if indeed you suffer from worn bearings.

I would look for  pump that has a higher pressure rating. It basically means a combo of larger impellers, and a bypass valve with a heavier spring and will deliver higher pressure before it bleeds off oil back into the pan.

If that makes no sense, ping back questions. There's plenty of cerebral horsepower to get you answers you need.