Oil Pressure Issues

[DaPrato300]

I have a 62 C10 that an ole farmer just rebuilt a 350 and put into it. The motor is said to have only 250 miles on it. At idle the oil pressure will sit around 40psi. Once I pull off the brake it will drop to about 10psi and then climb back up to around 30psi. Any ideas why this would happen?

[MacAttack]

Is your idle speed too quick? How old is your sender and gauge system?

Oil weight? Does the motor smoke at start-up?

[DaPrato300]

The truck usually idles around 900-1100RPM. Whenever it fires up a small puff of white smoke will come out, but then agian when I leave for work it is about 30 degrees outside. I am going to change the oil tonight when I get off work and prolly pump some lucas through it. Sender and gauge system.. shoot I have no clue I havent had this truck to long few weeks at the most so I havent really dug into it all to much.

[markeb01]

Not clear what you mean by "pull off the brake". Are you running an automatic transmission, and/or do you have a vacuum brake booster? Putting a sudden load or having a vacuum leak could suddenly lower the engine rpm enough to drop the oil pressure. Maintaining 30-40 psi at idle indicates it's in pretty good shape. If it was only generating a consistent 10 psi at idle, it would indicate excessive bearing clearances, a tired oil pump or a weak pressure spring in the pump. If the engine has truly been rebuilt and only has 250 miles on it, the rings may not have seated yet and could be responsible for the puff of white smoke. White or blue is usually oil, black is generally gasoline.

30 degree temperatures have a habit of bringing out a few "features" that wouldn't be noticed if the temps where in the 70's.

[DaPrato300]

I am kind of leaning towards the oil sending unit and/or wiring. The truck runs great with no lifter noise. To me it doesnt seem like the truck is starving for oil. oil when I release the brake and push on the gas from a dead stop does the oil pressure drop down to 10 psi. I guess I will find out tonight when I start tinkering with it.

[MacAttack]

Priority One is what the oil pressure indication is at 45 mph - if your gauge is good. Is it electrical, as it would appear from your "sender" comment? I never trust those things - oil or coolant - mechanical is just to reliable, especially with metal lines.

Mac.

[DaPrato300]

FOUND MY PROBLEM!!! so come to find out I have a pressure line for the oil pressure and the smart guy that designed this cheap clear plastic line didnt take heat into account because it is brittle and melted and is now squirting oil everywhere. Damn the luck for a $1 piece of plastic to break the truck.

[MacAttack]

SCORE!

[dan76]

Originally Posted by DaPrato300

FOUND MY PROBLEM!!! so come to find out I have a pressure line for the oil pressure and the smart guy that designed this cheap clear plastic line didnt take heat into account because it is brittle and melted and is now squirting oil everywhere. Damn the luck for a $1 piece of plastic to break the truck.

The factory line was metal and rarely had issues.

[Captainfab]

You can replace that plastic line with a copper line. Much better IMO.

Originally Posted by DaPrato300

FOUND MY PROBLEM!!! so come to find out I have a pressure line for the oil pressure and the smart guy that designed this cheap clear plastic line didnt take heat into account because it is brittle and melted and is now squirting oil everywhere. Damn the luck for a $1 piece of plastic to break the truck.