Another Oil Pressure Thread

[k20_chevy]

Hey guys, Im troubleshooting low oil pressure. I found a few threads on here but none seemed to end with a resolution.

My sb350 runs at 45-60 psi oil pressure when cold but when the oil warms up and the trucks in gear I got about 5 psi. When I drive it goes to about 20 psi. I'm currently running Mobil 5000 with 10w-30 oil.

I changed the oil and oil pump but still have the same thing. I have a mechanical oil pressure gauge and tried a spare I have and they read the same thing. It was a melling oil pump from AutoZone that I bought. I'm not sure what to do.

I was going to run a quart of motor flush through the oil to see if there is a clogged port I don't know about. My thought was try another oil pump like the one in the first link below and try 10w-40 and lucas. I really don't want to spin a bearing or something cause of low oil pressure.

Any thoughts??


Melling M99HVS

Melling M55HV

[stumpuller454]

i would just try some 10w-40 + lucas, if you don`t have any unusuall noises or ticking shes probly just well worn in..... you could possibly try a 20w-50 or a 15w-40,

you could put in a high volume pump but there is still the inevitable later on...

[bradrhale]

if you decide to do a flush on the oil system, be ready to drop your pan shortly afterwards. the last time i seen that stuff, a quart costs a few dollars. a gallon of diesel costs 2.50. you can drop the oil and put in the diesel that way but never run it above idle. done it before with excellent results. however, the junk in the bottom of the pan would have clogged up the pump in no time.

[k20_chevy]

I know a some chevy's run low oil pressure but mine has hit zero on a few occasions.

bradrhale - what reason did u use diesel as motor flush? was it for the same purpose im trying to accomplish?

stumpuller454 - what the inevitable? A rebuild?

[bradrhale]

diesel will dissolve crud but still has enough lubrication in it to keep the engine cooled and oiled.

[leolkfrm]

how was the oil filter bypass valve?

[k20_chevy]

Originally Posted by leolkfrm

how was the oil filter bypass valve?

I don't know what that is.

[leolkfrm]

some the valve is driven into the block, if if doesn't close all the way it will reduce oil pressure when hot

[k20_chevy]

Is this something that can fail overtime. Can i replace this part?

[k20_chevy]

Originally Posted by leolkfrm

some the valve is driven into the block, if if doesn't close all the way it will reduce oil pressure when hot

Well mine looks just like this. I didn't see anything wrong with it. My truck had always ran at 5 psi in gear warmed up since i got it. I don't have anytime time till the weekend but I will try the diesel fuel idea to flush the engine, maybe there's dirt somewhere.

Then new filter with 10w-40 and lucas and see what happens.