oil pressure light

[Tractorat]

Anyone know just how low a gm car has to get on oil to light up the low oil pressure light ?

(dont ask)

 

[Bob4x4]

I have seen some switched at 7psi

 

[Tractorat]

The situation is that a friend of my wife's is driving across country in hot weather, probably at 80mph or higher. The other day her oil light came on. She put some oil in in and the light went out. Knowing this woman, she could have been driving it low for days. There is probably no answer here. But I was just curious how low the oil has to get to turn on the oil light.

 

[hcole]

I use a GM oil pressure switch for my Fass teed into the line from the VP44 inlet and then to my gauge in the cab. It brings the light and chime on at 5 Psi.

 

[Tuesdak]

9 PSI on a Duramax and GM is known to "buffer" the "Low Oil pressure stop engine" alarm. Say when you ruin the CJ4 oil and shifting from park to drive causes a sudden low oil pressure spike. So GM delays showing the light or alarm depending on the year to indicate a true engine damaging condition.

To trigger the light the oil has to be so low the oil pump sucks air. The rest of the oil in the sump likely will be ruined from stress and overheating aka hitting hot bearings that are burning up from lack of oil with loss of cooling due to low level in the oil pan. Luck, no/low damage, would be momentarily uncovering the oil pump pickup in a turn or acceleration/braking.

The ruined oil needs to be changed and the old filter cut open to see how bad the damage is. Check for sludge.

I would say the source of oil leaks or consumption needs to be found, however, IMO the engine has been damaged from loss of oil pressure. Figure on rebuilding the engine or unloading the vehicle while it still runs. Doing UOA on oil after the change could rebuild trust in the engine - just not likely to be lucky with oil pressure loss for any amount of time.