Flashing red oil light and buzzer = low coolant?

[ScienceBoy]

Sorry Ads, haven't been on for a while. I've never solved this completely but I did solve the boiling over (vent on t-stat housing blocked and air in system). Ours comes on after driving for best part of hour. It comes, and goes, and comes, and goes. There are no leaks, well not dramatic ones but hey it's an 88, and the oil level is good. The oil pressure sensors are new.

So it's either the oil I put in was too thin and that has an effect at high temps (and it was thinner than it should have been, my error, but not much.
Or there's an instrumentation issue, but why at higher temps?

I'll use thicker oil next service, but one solution may be moving to an oil pressure gauge to see what's really happening rather than just the buzzer of doom. So we're driving around with a nuisance alarm on a critical instrument. As long as it goes off after a couple of seconds I feel ok for now. If it goes on for longer, pull over, switch off and check it out!!!

[ScienceBoy]

Could still be loose wiring too...

[Ads1987]

Have you actually had the oil pressure tested?

Thanks for getting back to me that's really helpful

[ScienceBoy]

The way I see it Ads, if I had a true low pressure, I'd have a loss of oil. That's what it's guarding against, a catastrophic loss of oil. So....

[Ads1987]

Fair enough, i'm hoping i'ts a similar fault to mine so going to change the sensors and have a bit more of an in depth look at the wiring.

Thanks for your help

[Timwhy]

The high pressure sensor in the front of the engine may need a new wire and spade to the connector at the top left of the motor. Mine was severely corroded and would intermittently set off the buzzer. Replaced the wire and cut into the connecting wire about two inches back from the equally corroded connector.

[ghost123uk]

Have you actually had the oil pressure tested?

The way I see it Ads, if I had a true low pressure, I'd have a loss of oil

Sorry to butt in, but the above does not compute. You can have low oil pressure and not lose any oil at all. The two are not connected.

[marlinowner]

If the oil pressure light only comes on when the engine is hot, to me this implies marginal oil pressure. Either oil is too thin, oil pump is worn or main bearings are worn. Low oil level would show as oil pressure light coming on when oil level goes below oil pump pickup, eg due to oil running to one side of sump whilst cornering. Roundabouts being classic.

[ScienceBoy]

Sorry to butt in, but the above does not compute. You can have low oil pressure and not lose any oil at all. The two are not connected.

Feel free, but please add a reason/explanation to the comment. My new pressure sensors would agree with your statement as I said; low pressure with no loss of oil.

But that's the primary reason for the sensor. In a sealed system, the primary reason for loss of pressure is loss of containment.

E D I T: the reason is the engine is not a sealed system, only parts are under pressure.

[ScienceBoy]

The high pressure sensor in the front of the engine may need a new wire and spade to the connector at the top left of the motor. Mine was severely corroded and would intermittently set off the buzzer. Replaced the wire and cut into the connecting wire about two inches back from the equally corroded connector.

Cheers Tim. As I've noted some way back I had issue with a connector at the top left. I was doing what you say and some souldering mad it better (ish). Perhaps I'll have another go at it. Cheers.

[ScienceBoy]

Still getting BoD, but feel it's definitely engine not creating pressure at high temps. Is always corrected for a short while by a dap of clutch in accelerator. New oil soon.

[phil_b]

Hi, been looking at this with interest as I have an intermittent but different oil light issue. Mine comes on momentarily and then goes off even before the engine is started?
But going back a few posts up, there seems to be some confusion over the purpose of the oil pressure lights, as has been said they are there to warn of low pressure, usually due to wear in related components and which causes further engine damage and wear and ultimately failure. They will also warn of significant or total loss of oil as no pressure will be generated at all. However low pressure due to worn out components etc can occur regardless of oil level, it is quite possible to have poor oil pressure even when the oil level is full, so checking oil level when a warning occurs only confirms oil in the system but does not rule out an oil pressure fault.
My thoughts from what you have posted is that your symptoms do point towards a genuine low pressure issue, ie an engine fault rather than a warning system failure, this is because you have checked or replaced most of the warning components and the warnings do seem consistent with an alarm of the high pressure/revs part of the system which is also more likely to occur at higher temps, and will stop when the revs are reduced.
I think your idea of fitting a oil pressure gauge is a good one but sooner rather than later.
Hope you get it sorted.
Cheers Phil

[ghost123uk]

Phil, "we" have been saying that from page 1 of this, but Mr ScienceBoy ain't being very Scientific about understanding oil pressure and oil pressure warning lights etc.

[ScienceBoy]

Ok, ok, ok, oil pressure was checked at post 20, and I've just had it checked out by another (very good) garage (imho) and they found the oil pressure aok.

Next step to change that high pressure switch for a new one plus sender and gauge. Mechanic reckons that's the more likely cause than oil pump wear, and easiest thing to eliminate.

[ghost123uk]

Good lord, it's nearly a year later now