How low is too low - oil psi

amcdonald

amcdonald

Active Member
OK. So go for a little spin and get everything warm. Stop at a traffic light. How low does the oil pressure need to go before one might expect trouble, ie catastrophe? 3500S NADA style.

I am green when cold, but hot it is looking ropey :(

108k so not an entirely surprising situation but otherwise idles smoothly, bit noisy but with no carpet it would be!

I decided to spend money on paint not engine. A gamble.
 
I would not be hugely concerned, it is normal on hot idle to be at 1/4 or less deflection, so long as when you are driving it increases to over 1/3 I would say its healthy.
On many cars and in particular lazy V8's you could expect the engine to run satisfactorily for many years with less than 10 psi, once the oil pressure light starts to come on would be the time to start planing a bearing shell replacement and oil pump inspection but even then if its a slow and gradual decline in oil pressure you could happily drive it for a long time still.
If you are concerned you should get an accurate mechanical oil pressure meter and determine the true psi at hot and cold and if you feel it warrants some expense some remedial action could be taken however were it mine I would likely time it to coincide with rings bearings and cam shaft rocker replacement time.

I am sure other will comment soon.

Graeme
 
Hi Adrian,

The oil warning light will come on and stay on when the oil pressure drops to within the 7 to 10psi range or lower. Does your oil warning light come on at idle? Does the engine knock when first started? How often is the oil normally changed and when you look inside the rocker cover with the oil filler cap removed, what colour do you see? Is it a shade of brown or more black?

Ron.
 
I think our NADA V8's have failure prone oil pressure senders - the previous owner of my car - 20 yrs ago - commenced a rebuild on a perfectly good motor because of a false gauge reading (and the rebuilder did a crap job!)... also, check the wiring carefully.......
 
Thanks for the comments. Actually there are no outward signs of trouble other than the gauge, although in a new development I did have a concerning lack of power going up a not huge hill lately. I thought I was slowing a bit, then I realized my foot was flat on the floor. Hmmm. I will take a look at the fuel system as i had trouble there before.
Cheers
 
Very common symptom of fuel vaporization especially evident driving up steep inclines.

Graeme
 
My NADA runs at around 30PSI when hot and driving, but at tickover, the gauge pretty much goes to zero. I have changed the gauge and sender but it made no difference. The oil light never comes on. I have done 2000 miles like this with no nasty noises so I have decided to stop worrying. The original NADA handbook says the gauge will drop into the red when hot and not to worry. Apparently this is why the red/green stripe on the gauge was replaced with a white line!
 
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