Oil light

On Saturday I drove to a location about 30 miles away. Approximately 2/3’s of the way to my destination the oil light came on, flickered off and on and then stayed on for the rest of the trip. When I left this destination I checked the oil, it was almost full. I drove home and the same thing happened.

I had been checking the oil more often and looking for leaks on the garage floor because it had been leaking. But the distributor seal was replaced in January and that solved the problem. So I felt pretty confident that there was not an oil leak.

I took my car to a mechanic Monday who checked the oil pressure(it was ok) and replaced the sending unit. In the evening I had another 30 mile drive, but the same thing happened that happened on Saturday.

I have a 1995 Toyota Camry with 143K miles on it.

You’re taking a huge risk by driving with the oil pressure warning light on. According to the information you provided your mechanic did the right thing by checking the oil pressure. The problem is that now the new oil pressure sending unit is telling you there’s not enough oil pressure. This is not a good thing. Engines with insufficient oil pressure can destroy themselves within a few miles.

Thanks for your reply. So I take it when I check the oil with the dipstick and it is nearly full, it doesn’t really tell me what I need to know. How is insufficient oil pressure corrected?

If the oil pressure is not high enough there is a problem with the oil pump or some other component of the lubrication system.

If your mechanic measured the actual oil pressure, with an calibrated gauge, there may not be such a problem, but you can’t gamble on it if the oil pressure light is on. The light means the sender is measuring oil pressure that is too low for safe engine operation.

Thanks again. Yes he did use a calibrated gauge to measure the oil pressure and will take it for the same drive I took yesterday to see what the engine sounds like. He thinks it is in the dashboard circuit system. I appreciate your detailed and informative response, very helpful.

As a follow up, my mechanic removed the oil pan today and cleaned and inspected the oil screen. He also changed the oil and filter since it was soon due anyway. He found no plug and everything was pretty clean he said. Does this mean the problem is not the oil pressure?

If the calibrated gauge showed good pressure, chances are the sending unit is faulty. Did he change it out yet? They should be available inexpensively from his supplier.

I think he may have seen a problem with the oil pressure and decided to drop the oil pan to find it. The oil pump system also includes a pressure relief valve that should be a part of the oil pump and may be faulty. This may require a replacement pump.

Let us know what else develops.

The sending unit was replaced after the first time the light came on and it made no dfference. The light did the same thing the next time I drove 30 miles. He decided to check the pan rather than test driving it because to drive long enough for the light to come on would have been 2 hours anyway and he felt it was both more certain and potentially less expensive to just pull the pan. He did not say anything about the pump but I will ask him. I have to drive 300 miles this weekend and he doesn’t want me to use my car just yet for that long of a trip. So I have another for that trip.

Thank you again. I did not realize the oil light meant oil pressure, I thought it meant oil level and I was confident there was enough oil in it. So I am very grateful for that important distinction, I was lucky this time.

When the oil pressure was tested was the oil pressure noted after the car had been run for a while?
Do you know what the pressure reading was?

Since the sending unit was replaced I think you can figure on one of two things. Either the oil is getting very hot due to extended driving and oil pressure is lost due to worn crankshaft bearings or there is an intermittent short in the wire from the dashboard oil light to the oil pressure sending unit.

If a wiring problem was the cause this should occur at anytime and not occur only during extended driving spells.

One thing I think should have been done is this. You say the mechanic dropped the oil pan, etc. While the pan was off he should have dropped a crankshaft main bearing cap or two and checked whether the bearing overlay was disappearing. This would have only taken a few minutes and could have verified whether the problem was related to something serious like crank bearings.

If the bearings were worn then it’s possible to install a set while the oil pan is removed.

If the oil light in only illuminating during a somewhat lengthy drive then I suspect the crankshaft bearings are worn.
Another possible cause, but less likely, could be worn camshaft journal surfaces on the cylinder head. Badly worn surfaces here can cause an oil pressure drop.

My mechanic says that there would be a noise in the engine if the crankshaft bearings were worn. He is proposing that he take the car for a lengthy drive to listen to the engine without charging me for his time. He used a mechanical gauge, which he prefers, not a calibrated one to check the pressure. I don’t know what the reading was, he ran it for 20 minutes at a rate that it would run if one were driving 65 mph.

I’m disappointed he didn’t check the crankshaft bearings or camshaft journal surfaces while the pan was off.

I agree that there is a pretty good chance that you don’t really have an oil pressure problem. Still, if you and your mechanic are wrong, that’s likely to be one expensive misjudgement.

What I’d do, and your mechanic could probably do, is to try to plumb a splitter that allows the oil pressure sensor to be mounted outboard from the engine and also feeds a mechanical oil pressure gauge temporarily mounted under the dash. I’m not one hundred percent sure that the necessary fittings can be found off the shelf, but they probably can. If your theory is correct, the mechanical gauge will allow you to confirm that the oil pressure light is whacko. At that point you can try to fix the electronics (not cheap probably) or apply black tape (cheap) to the oil pressure warning light and depend on the gauge – which you will have learned to read – instead.

When the mechanic checked the oil pressure with a gauge, I’m hoping he checked it under the same circumstances that were present when the light came on—fully warmed up and both highway and idling speeds?

If the oil pressure is indeed OK, possibly look for a wire from the sender that is chafed and intermittently touching ground.

Your mechanic is incorrect by stating there would be a noise if the bearings were worn.
A bearing knock can develop when a bearing becomes excessively worn but bearings that are worn to some degree across the board can cause an oil pressure loss and not make any noise at all.

Most bearings are set up with .001-.002 of an inch oil clearance when new. When worn this may increase to .005 or more. Oil pressure will be lost but it’s unlikely to make noise. When the clearances start getting up into the upper end of the single digits then noise may start in.

If this oil light is only flashing on at idle speeds then I tend to believe it’s a bearing problem. If it flashes on at highway speeds it could possibly be a wiring fault.
While I don’t like the stuff, you can try adding a bottle of STP oil treatment to the engine oil. This will thicken the oil up. If the oil light stays off then it boils back down to a bearing problem. Hope that helps.