Oil light remains on

[Boris64]

Hi, back for more advice please.

I'm about to change the gearbox and will address the insistent oil light while I'm at it.

Assuming it's wear in the oil pump (which seems likely given vintage and the junior mechanic's love of high revs), are there repairs/improvements possible to the oil pump, or is replacement the easiest/best option?

Thanks

Pete

[drivewasher]

Is light on all the time?
How long has it been on, if for a while I would expect engine to be knocking
Have you ruled out a faulty/blocked oil pressure switch?

[bmcecosse]

It will NOT be the oil pump.....although it may well need renewing as you rebuild the engine.. Check the switch first. And possibly (but very unlikely) the relief valve... Drop the sump and inspect the big ends - and the centre main...

[Boris64]

Thanks for quick inputs.

The light does the normal on with ignition, off as engine runs then starts flickering until permanently on after about 5-10 miles.

Engines using a bit of oil but certainly nothing drastic and no appreciable knocking other than usual tappets.

Could it be as simple as a faulty switch that can't deal with the increase in temperature?

Thanks

Pete

[bmcecosse]

You can try that - even better - fit an oil pressure gauge. What oil are you using? You can try an oil and filter change - but what you describe almost certainly needs a crank regrind, and new oil pump......

[biomed32uk]

Seconded - you could try another switch for the cost of it and the simplicity of changing it, mine failed but was completely open, no light at all.

As BMC says, an oil pressure gauge is probably the best thing you can fit, an excellent window to the health and condition of the engine, by the time the oil light comes on when theres a problem it is too late normally.

By what you describe if it is not the switch then the bottom end of the engine is well worn.

[katy]

Another possibility is that the pressure relief valve is stuck partially open, or it's spring is weak or cracked.

[Boris64]

Thanks for the advice.

I'll try the switch and take a look at the relief valve as a start.

I'll have a look inside when I change the gearbox.

Can you/anyone advise how the oil pressure is generated via the bottom end bearings/crank?

Thanks

Pete

[kennatt]

Thanks for the advice.

Can you/anyone advise how the oil pressure is generated via the bottom end bearings/crank?

They don't,they restrict the flow from the pump which holds the pressure high,when they wear the gap between the bearings and the crank becomes too wide and allows the oil to flow out too easily,and the pressure drops because there is nothing to hold the flow of oil. This then lets the bearing come into contact with the crank and the wear gets faster,and eventually they come together and knock.The high pressure holds the bearings and crank apart.Once the gap becomes too wide There's nothing much can be done to improve the pressure,needs regrind and thicker bearings . It only takes One big end or main to wear and down go's the pressure.

[Boris64]

Kennatt

Many thanks for the explanation, I would never have worked that out but it makes perfect sense.

Pete