Below Spec Oil Pressure

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Mar 27, 2003
Georgia Tech
New 10w-30 oil + oil filter.

While driving, I can watch the oil pressure gauge drop as the truck warms up to highway cruiser temp, until the gauge hardly registers at all.

FSM Spec:
With engine at operating temp,
Idle: 4.6 PSI or greater
3000rpm: 36-71 PSI

Not trusting the gauge, I hooked up a mechanical gauge today. Warm, but not hot, the pressure at idle and 3000 rpm test to right in the middle of acceptable ranges.

But, as the engine warms up to hot, the idle drops to 3-4 psi (bouncing needle) and at 3000 rpm pressure drops to ~30 psi.

Obviously, these values are not good. I am not sure what to do to correct the issue.

Should I try 20w-50? (worked for low pressure on my '74)
New oil pump?



Check this thread for background-
From what i know using higher weight is just a band-aid for a bigger issue, but you could try it and see what your results are
I have always thought of higher weight oil as a bandaid as well, but it is a bandaid that has kept my '74 running for the last 6 years.

Still I don't really consider that a 'fix'.

Anyone else have input?
Sounds like the oil pump.

I could be wrong here Ken. Heck I quite often am, but if the pressure is fine at idle and 3k rpm when the truck starts what would lead you to believe that the pump is the culprit once the truck warms up?

I think it is probably something other than the pump and my thoughts ain't exactly positive in that regard. [shudder]
I think it is that itty bitty oil pressure relief spring setup that Robbie told us about many moons ago. How's that for tech? But seriously search for stuff on that one and you might have found the fix.

Search is your friend not mine......................:flipoff2:
Search is your friend not mine......................:flipoff2:

Haha, that's why I linky looed for you you bum! :D:D:D

Here it is again:

Actually, I have a huge folder of favorites saved which are almost entirely gems of experience and expertise from Robbie over the years so my search took about two seconds, still there might be more on it if one searches. It seems a simple fix or at least a simple way to work one potential problem out of the picture here. :cheers:

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