Engine: oil light

[doublepaddle]

'57 Transtar. My idiot light for oil pressure came on a couple miles from home. Found out I was a little down on oil. Topped up and restarted the truck. Light still on. Have not used the truck for 2 weeks. Started it up and light still on. Have not tried to drive it anywhere yet. 12k on rebuild and new switch at that time. Oil switch came from Napa (China?). Any ideas?

[jclary]

My idea is for you to get an oil pressure gauge and find out exactly what kind of oil pressure you have! I have had oil lights go out with as little as 12 lbs of oil pressure. It could be a defective sending unit, or something in your wiring causing the problem, but before risking engine damage for lack of oil, I would take the trouble to confirm with an old style pressure gauge.

[52-fan]

Check and be sure the wiring is not off the terminal or grounded somewhere. I washed an engine once and had the oil light on when I started the engine. The washer had knocked the wire off and it was touching the block.

[Lynn]

So, 57 transtard doesn't have a gauge, just a light?

Senders can go bad. As John said, put a mechanical gauge on it and find out what your oil pressure really is.

[Steve Winzar]

If you do check your pressure with a gauge, also check the strength of the oil pressure relief valve. This happened to me years ago with a '73 Triumph Stag V8- after having the engine expertly rebuilt after buggering up its bearings and crankshaft it was back to the shop within days with the red light creeping on again as the oil thinned. The 'experts' did not see that one coming - the pressure would go down to only 7 PSI. New spring installed and all was well again.
Check and or replace your spring.
Regards Steve W

[Bud]

Most oil pressure light switches are set to come on around 4 to 6 lbs pressure. If the oil pressure light only illuminates at idle when the engine is hot, that isn't the end of the world, but if it is illuminated at driving speed, there is a problem. All of the above posters are correct with their comments. I've seen grounded wires and bad switches causing the light to come on, but a mechanical gauge should be substituted for the switch to be sure that the engine does have adequate oil pressure. Bud