Oil light

[biscuit]

Hi All, I had my BMC reconditioned 18 months ago all seems to be ok, however on travelling through a tunnel I noticed my oil light is flickering at low revs. I travelled for a further 6 hours non stop and all was good?. The temperature was a steady 80 all day. The oil level is not low, if anything a little high. Could this be the oil pump?.

I have basically no knowledge of maintenance.

 

Thank you.

 

Edited April 11, 2023 by biscuit

[Tracy D'arth]

Not uncommon on a BMC.

1.5 or 1.8?

 

As long as it goes out promptly on start up it will be fine. 

Likely that the pressure switch on the engine is a bit sensitive, try a new one. The on pressure can be from 5psi to 20psi I have found.

If it is genuinely low pressure ensure that the tick over is 750 to 800 rpm, that the the oil is fresh, 10W40 or if you like 20W50. The  bit thicker will help but its heavier to start in winter. Check that the engine is not overheating.

I have known these engine run with the oil light full on until you rev them and they still run for years.

[bizzard]

6 minutes ago, biscuit said:

Hi All, I had my BMC reconditioned 18 months ago all seems to be ok, however on travelling through a tunnel I noticed my oil light is flickering at low revs. I travelled for a further 6 hours non stop and all was good?. The temperature was a steady 80 all day. The oil level is not low, if anything a little high. Could this be the oil pump?.

I have basically have no knowledge of maintenance.

 

Thank you.

 

Too much oil can cause the oil to become hotter and thinner, lowers viscosity, more of it in contact with the hot engine block. A 20/50 oil would be better. Oil pressure switch might be faulty.

 

9 minutes ago, biscuit said:

Hi All, I had my BMC reconditioned 18 months ago all seems to be ok, however on travelling through a tunnel I noticed my oil light is flickering at low revs. I travelled for a further 6 hours non stop and all was good?. The temperature was a steady 80 all day. The oil level is not low, if anything a little high. Could this be the oil pump?.

I have basically have no knowledge of maintenance.

 

Thank you.

 

 

[Tony Brooks]

I am with change the oil pressure switch first because they do go flaky, and they are relatively cheap. Once that is ruled out things tend to get very expensive.

[Kudzucraft]

You can put a T in the line and add a mechanical gage along with the sending unit.  That way you can check that actual pressure.

 

Restoring an old wooden Chris Craft and I am adding a gage, on the motor just so I can see what the actually pressure is. 
Just bought a tractor with a 3 cylinder diesel and does exactly as you describe.  So I put the gage on it to check and it still had pressure when the light came on.

[Wanderer Vagabond]

I'd also go with it being a faulty oil pressure switch. It was the first thing that failed back in 2013 when I got the boat and my first reaction was, obviously, switch off the engine. Called out RCR (newby at the time and not au fait with boat repairs) and when he showed up he asked me if there had been any untoward noises, when I said "No", he said it was probably the oil pressure switch and fired up the engine. It ran with no problem and the new pressure switch was a doddle to fit. Good experience because a month later the the water temperature sensor failed so that got changed as well

 

ETA Oh, by the way, welcome to the forum.

Edited April 11, 2023 by Wanderer Vagabond

[john.k]

Quite common for 1970s Perkins to run with near zero oil pressure .....the motor in my now disused truck ran for 20 years without troubling the oil gauge.......its replacement was a Leyland with a 640 V8 Perk ,and its only got oil pressure if its revved cold......having had Perks for 60 years ,I dont worry provided the oil level is good ........Incidentally ,broken pipes on oil pressure gauges have wrecked more motors than low oil pressure....always use an electric sender /gauge combo.

[Tony Brooks]

1 hour ago, john.k said:

Quite common for 1970s Perkins to run with near zero oil pressure .....the motor in my now disused truck ran for 20 years without troubling the oil gauge.......its replacement was a Leyland with a 640 V8 Perk ,and its only got oil pressure if its revved cold......having had Perks for 60 years ,I dont worry provided the oil level is good ........Incidentally ,broken pipes on oil pressure gauges have wrecked more motors than low oil pressure....always use an electric sender /gauge combo.

 

I would add that an oil pressure gauge, especially electrical ones, have probably caused owners far more angst than a simple oil light. As John says, many engines, especially older designs, will run happily for years on a lower oil pressure than that in the manual, especially in inland boats where the loading is so low for most of the time.