Hi all,

Driving home today and the oil pressure light started to come on intermittently. First appeared as I slowed out of 110km zone into an 80. Disappeared when I went up a rise at 80km/h and came back on on the flat. Also went away on a right hand bend. Now I'm thinking the oil level must be really low...

So I've stopped and checked all the fluid levels and they are all good. Restarted and drove to the local and picked up a 1L of HPR 10 just in case the oil levels dropped while cool.

So it's been over an hour and no change in levels and the light is continuously on while sitting in the driveway.

Anyone experienced this? Any thoughts or suggestions?

Sender units do this sometimes when they fail......but get it checked soon as you can.
Its a low pressure light not low oil.

Sender units do this sometimes when they fail.....

Great suggestion, thank you.

I can't find mention of it in the workshop manual. Any suggestions for parts numbers and possible tests?

Basically, if you are doing 110 kph with the oil light on, and the engine doesn't seize up on you, you can assume oil pressure is ok but the pressure sender is telling lies.
I've known someone who drove their Magna until the light came on, assuming it was an oil level indicator. Often called an 'idiot' light, for obvious reasons.
No test possible, just replace.

As others have stated, it's most likely the oil pressure sensing system - but it is quite possible there's a serious internal problem with your engine.

DON'T drive your car. On the off chance your oil pump has failed, or a bearing is toast preventing oil pressure from being developed, you'll junk the engine really quick. It may already be too late.

If the oil light comes on in anyone's car - they should turn it off ASAP, check the oil level, and if the level is okay, get it towed.

Actually, if the oil light comes on at 100 kph and it is really due to low oil pressure, the engine seizing after about 10 seconds should be a good indication there is a problem. lol

Sigh.

Engines can run for many hours with low oil pressure (such as caused by a chewed out bearing), damaging the engine but still running. Even a complete oil pump failure can see the engine running for quite some time, especially in a liquid cooled engine.

Telling someone to keep running their engine because it "hasn't stopped" 10sec or even 10 mins after the oil pressure warning light came on has got to be the worst advice I've seen for while. I've seen one engine with destroyed crank journal and low oil pressure run virtually without any symptoms for about 5 hours before it was torn down and the problem discovered.

It was bin fodder - and all because the light was ignored by someone who said "seems like it's still running okay, must be a bad sensor".

To the OP, don't drive it as is. Change the sensor (as this is very likely to be your issue) and then go from there.

Fair enough. Better safe than sorry.
I've only had one experience with an engine that dropped oil pressure through a low oil level, it was bin fodder anyway.
I'm guessing a Magna at 100 KPH that drops oil pressure to the few PSI it takes to make the oil light flicker will be junk engine wise no matter how quick you can stop and switch off.
In other words, if the light flickers at 100 KPH, either the sender is U/S or the damage has already been done. Pistons overheating due to a lack of oil cooling, scored pistons, seized rings, crankshaft and camshaft journals picking up bearing material, etc. The engine ends up noisy, down on compression and power, oil consumption up, etc. Us old blokes used to fit an oil pressure gauge to our cars and kept a close eye on oil pressure. When the light flickers and it really means it, it is 'oops, too late, engine is toast!'

So basically I'm saying:
Light flickers, no worries, just the sender.
or
Light flickers, no worries, your engine is toast already and you will need a new one.

Sigh.

Engines can run for many hours with low oil pressure (such as caused by a chewed out bearing), damaging the engine but still running. Even a complete oil pump failure can see the engine running for quite some time, especially in a liquid cooled engine.

yup. this 100%
I have personally driven an old datsun for almost 3 months with low enough oil pressure the light would flicker at anything below 1500rpm.
(I didnt care if the engine died, I had a spare)
I also used to work on a bus (one of many) that ran for almost 4 years with extremely low oil pressure.
In both cases, even though they went on for a very long time, when they failed, they junked themselves pretty badly.
Oil pressure senders are cheap, just replace it.
Also, if you can get a cheap mechanical gauge, it makes for a real simple 'pressure tester'

FYI, low oil pressure can also be caused by the pressure releif valve being stuck or damaged, however the end result is still the same. Insufficient pressure = Increased wear on bearing surfaces

I have personally driven an old datsun for almost 3 months with low enough oil pressure the light would flicker at anything below 1500rpm.
(I didnt care if the engine died, I had a spare)
I also used to work on a bus (one of many) that ran for almost 4 years with extremely low oil pressure.
In both cases, even though they went on for a very long time, when they failed, they junked themselves pretty badly.


Yes, I've stretched the life of an engine that had low pressure and flickered the light at hot idle and ran it until it died. Thicker oil plus STP, that sort of thing. But I knew it was worn and would junk itself eventually so no great loss.
However, the OP says the light is flickering at 110 KPH. A big difference. If the oil pressure really is 3 to 5 PSI, a seized con rod or main bearing, or seized camshaft is just moments away.

DONT DRIVE THE CAR, DONT START THE CAR, DONT RUN THE CAR

I have seen this a few times in the past, have had to replace a few engines as well

Get it towed to a shop, get them to put a manual pressure gauge on the engine and run the engine upto FULL operating temp and check the pressure

Sadly these engines do have an issue with the pressure relief valves sticking and causing oil pressure to drop and then engine damage can be done.

As your light is coming on when engine revs drop and not simply randomly there is in my opinion a serious issue

A stuck pressure relief valve I've come across before, but that tends to be ok pressure wise with the revs up. On the old Sigma a stuck pressure release valve would have the light on at idle and up to 1,500 rpm, but go off above that.

Never mind, good advice - better safe than sorry. Get a pressure gauge on it to identify the problem.

Mal, what are the chances of a 3.8L engine surviving near zero oil pressure incidents at 110 KPH?

The chances are hard to say, if was a few seconds at idle generally not too much an issue, if a constant thing then very little chance. I have 2 of these down the back where the issue above was present, both engines sound like ticking time bombs.

Remember the tolerances are much tighter in these than an old sigma, you can not compare an old astron to these motors

I agree.

It's a point I was trying to make earlier, if the light goes on and it really is from low oil pressure at 110 KPH, the engine is pretty much ready to be pensioned off, no matter how quick you stop and switch off.

Hopefully it is just a failed pressure sender. A pressure check with a gauge will tell all.

Lots of warning lights on modern cars to tell you you have a problem that needs looking at ASAP. The oil light is one exception, it is more like an after the fact light, as in 'too late now, you had a problem, the damage has been done'.

Lot of people don't know that, and think it is more like a low oil level warning light.
(Lady at work relied on that light. When it started blinking going around a corner, it was time to add more oil.)