erke88

I have a 1971 Cutlass Supreme with a 350, 4bbl quad. I've been noticing that my oil pressure dummy light comes on lets say if I'm driving for a while and I stop a stoplight. My engine is sitting there at idle and then the oil light comes on. As soon as I push on the gas pedal the light goes off and everything is fine, but when I stop again the light comes on. Another interesting thing, when I put the car into neutral the light goes off. I've changed the oil to 20-50W hoping to solve the problem, but to no avail. I spoke with my mechanic and he said check the oil pressure switch. He said if its not that then it could be a sign that I have bearings going bad. Wanted to know what everyone on here thought, or if anyone had a similar problem and was able to correct it. Thanks!

RAMBOW

Go to an autoparts store and buy yourself a cheap mechanical oil pressure guage and hook it up to see what your oil pressures Really are at idle or running.

The idiot light sending unit activates the light when pressure drops below 10lbs, goes out above.

Recommended oil pressure is supposed to be 10lbs for each 1k RPM.

So check it with the mechanical guage to see how low it really is- and how much it goes up with rpm. ideal is around 40-50lbs cruising, but most of the time with an old motor you'd probably be bewteen 20-30lbs.

If your motor is original and never rebuilt, its likely worn out, causing low oil pressure. If your idle is really low you can try turning it up a bit, but that and using heavier weight oil is just a bandaid at best.

Means the motor is tired & ready for a rebuild.

That said, i've run motors with low o/p at idle (10lbs or so) for many many miles... Of course the O/P came up with RPMs. If it does not come up above about 20lbs, its likely ready for a rebuild.

MDchanic

The only "real" thing to do is, as Rambow says: go get (or borrow, or find in the garage) an oil pressure gauge, hook it up, and check to see what your actual pressure is, then do whatever you need to based on that information.

However...
The idiot light sender switch is cheap (should be less than $10 at the auto parts store - I just bought one on eBay for $2.50), nearly universal for GM cars from around 1960 to 1985, and extremely accessible and easy to change, sitting right out in the open on the left side of your timing chain case,
So...
You could always just change out the light sender and see if it still does it. If the light stops coming on, you can assume it was a bad switch, and avoid asking any deeper questions you'd rather not know the answers to.

citcapp

Don't cheap out on this, install a under dash mechanical oil pressure gauge and will you at it do all three oil/temperature/volts. You need to know whats going on with your engine. There is a reason their called idiot lights they don't give you any information

erke88

Thanks for the info everyone. The engine was rebuilt, but I have no information on when and cant get in contact with the previous owner because they changed their phone number. I'll do the above suggested...I really hope its not needing a rebuild. I just had the engine pulled and everything looked good, but then again I am not an expert. Thanks for the replies. Ill let everyone know how it pans out when I have time to check it.