James71Cutlass

Oil light came on today while driving so I came home and checked the oil. She’s full. Any reason why the oil light would come on?
Thanks.

jaunty75

The oil light comes on because of a loss of oil pressure, not a lowering of the oil level. You measure that with the dipstick.


I'm no expert here, but if this were my car, the first thing I'd do is replace the oil pressure sensor and hope that fixes it. They're a few bucks at the auto parts store, and they can go bad. But if the light still goes on even with the new sensor, then I would get an actual oil pressure gauge and hook that up. You want to know what the oil pressure actually is. If your engine is experiencing a loss of oil pressure, there are several possible causes. How many miles on the engine?

Sugar Bear

Replace the sending unit as suggested if there are no strange noises, the oil is close to full. Smell the oil for gasoline.

If strange noises don't run it.

What year, model, engine, mileage?

Good luck!!!

James71Cutlass

Thanks. I will do that. The car currently has a 307 in it. The original engine is waiting for me to pick it up but with everything that’s happening things are on hold.

mice driven it twice today first time 30 minutes light never came on. Second time it came on after 25 minutes or so. I just started it again to pull it into my garage. It didn’t come in at first but then did as I pulled it into the garage.

ill try changing the oil (haven’t done it this year) and maybe put something thicker in it. As long as it lasts this year that’s all I care about. The 350 rocket is going back in next winter.

James71Cutlass

1971 Cutlass S car. The engine is 307 out of an 80’s Olds. Engine sounds healthy, just picked it up from my mechanic today (replaced the radiator). He said it sounded strong. I’ll smell the oil. Thanks for the suggestion.

Sugar Bear

Is the light on all the time, not just idle? Cruising?

James71Cutlass

When I start the car it’s not on. Once I drive it, it comes on and stays on. Regardless if I’m at an idle or not.

Sugar Bear

Thicker oil isn’t the answer unless the sender is good and the bearings or pump are worn. In your climate 15w-40 is about the max viscosity I’d use.

Good luck and keep the thread updated.

Fun71

Well there's a problem that's separate from the possible low oil pressure issue. You can't let rodents have unlimited use of a motor vehicle as they will just go joyriding in search of cheese. Next thing you know the Wisconsin State Police will notify you they have impounded you car.

Sugar Bear

If it stays on above idle and sounds good, it’s probably just the sender. To rule out a short unplug the sender when the light is on, it should extinguish.

If there wasn’t enough pressure to open the switch at cruise I’d expect the engine to tap and or knock.

Good luck!!!

James71Cutlass

lol darn iPhone.

James71Cutlass

Will do. I’ll try that oil.

James71Cutlass

Thanks. I will try that. It’s always sounded good and the light just came on today for the first time. I may take it out tomorrow and see if anything’s changed.

jaunty75

If the car is cold when you start it, this is expected behavior. When the engine is cold, the oil is thicker and the pressure higher. Once the engine warms up, the oil thins a bit and the pressure decreases.

One question, what happens if you shut off the car after the engine warms up and then a minute later restart it? Does the light come on immediately?

James71Cutlass

I started it this morning. Took about two minutes for the light to come on. Drove it around and pulled into get some gas. Started it back up and the light didn’t come on for about 30-45 seconds. So no the light never comes on right away. Most of the time it’s 10 seconds but this last time I stopped after driving it for about 20 minutes it took 30-45 seconds to go on.

James71Cutlass

Which one is the oil pressure sensor?

James71Cutlass

Never mind I figured it out. It’s the lower one.

jaunty75

This sounds like what would be expected. A few minutes to come on when the car is started cold, less than a minute when it's started hot.

James71Cutlass

Do you think it’s the switch or the engine itself?

jaunty75

If you held a gun to my head, I'd say I suspect that the sender is OK and the problem is the engine. But like I said earlier, the first thing I'd do is replace the oil pressure switch. They're less than $10, and it's a five-minute job. Do that and then tell us if the light still comes on the way it did with the original switch. Until you do some actual troubleshooting, all we're doing here is guessing.

James71Cutlass

Ok thanks. I’ll do that along with changing the oil and maybe add a thicker oil.

Sugar Bear

I'm guessing the sender is bad, because it only takes approx 5psi to open the switch to turn the light off. If its been driven regularly at less than 5psi oil pressure it would be tapping or knocking.

As posted earlier, don't overdo it with thick oil, that can increase pressure but at the same time reduce oil flow/volume and make for hard cold starts.

Good luck!!!

James71Cutlass

Ok thanks.

James71Cutlass

Took her out today for about 45 minutes. Made a few stops. Mostly country driving with a bit of city stops and starts and the light never came on. Popped the hood after to make sure the sensor was connected, which it was.

OLDSter Ralph

What did you do ?

James71Cutlass

Nothing. Just got in and drove it lol. It’s really warm here today as well.

Tedd Thompson

A short time will tell if you saved 10 bucks or cost you a engine. Curiosity and economics alone wouldn't allow me to run a engine with a issue like that. Just me....... Tedd

James71Cutlass

I’m getting a new sensor put in when I get my gears changed in the rear end. This is also a temporary engine in the car. Do I want to blow it up? Nope, would I care if I did? Nope.

Greg Rogers

One thing I didn't see mentioned ( though maybe I missed it) is if the wire going to the switch has bad insulation or is pinched,etc, it can hit a ground and illuminate the light. I had that happen before. It can be likely on a car where the engine has been changed,etc.

James71Cutlass

Thanks. I'll take a look and yes this isn't the original engine in the car.