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Daimler LQ 3-24, flickering oil pressure lamp

Beat Weibel
Posts: 150
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Daimler LQ 3-24, flickering oil pressure lamp

Post by Beat Weibel » Tue Jan 07, 2020 1:55 pm

Hello experts

The oil pressure lamp of my 1934 LQ 3-24 flickers after some minutes of driving or idling. It goes out immediately after starting and I assume that oil pressure is ok but that it could be a failure of the oil pressure switch mounted on the oil filter.

Any expereince with that? Has anybody refurbished the oil pressure switch on prewar cars?

Best regards and many thanks for every advice
Beat

Stan Thomas
Posts: 575
Joined: Sat Feb 13, 2016 2:14 pm
Location: Penkridge. Staffs.

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by Stan Thomas » Tue Jan 07, 2020 2:54 pm

The oil warning light coming on at tick-over is not uncommon - in fact it says so in Daimler drivers' handbooks down the ages.

That it flickers after the engine has run for a little while is indicative of the oil thinning as the engine warms up. However, the warning light should NOT come on whilst driving at any speed in any gear.

Check the oil filter (I don't know what type on your engine) and check what grade of oil you are using if you are concerned.

Stan.

Beat Weibel
Posts: 150
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by Beat Weibel » Tue Jan 07, 2020 4:27 pm

Thanks, Stan for your advice.
Actually I am not overly concerned about the oil pressure as such since the warning light reliably turned off and stayed off during the whole summer even on the warmest days when the oil was probably most thin.
I just added a rubber washer between the housing of the switch and the electrical contact of the cable to prevent slight oil leaking, recently. Only since then the warning light goes on.
In any case, I will check the oil filter - maybe it´s stuck with dirt. I also thought that there could be some dirt around the switch that makes electrical contact (although oil is a good insulator).
BR
Beat
P.S. the engine is a six cylinder 3.3 litre (predecessor of the EL / ES 24 engines)

Stan Thomas
Posts: 575
Joined: Sat Feb 13, 2016 2:14 pm
Location: Penkridge. Staffs.

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by Stan Thomas » Wed Jan 08, 2020 3:33 pm

As the warning light works by "earthing" the connecting wire to the switch unit, it could be the rubber washer you inserted as a seal is causing some electrical resistance - just a thought.

ranald
Posts: 321
Joined: Sat Feb 13, 2016 8:21 am
Location: North Wales

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by ranald » Fri Jan 10, 2020 8:57 am

Hello Beat, Have you considered installing an oil pressure gauge? All the best, Ranald

Beat Weibel
Posts: 150
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by Beat Weibel » Fri Jan 10, 2020 10:55 am

Dear Ranald
I have thought about this but where would install the sensor? At the place of the warning light switch on the oil filter housing?
BR
Beat

ranald
Posts: 321
Joined: Sat Feb 13, 2016 8:21 am
Location: North Wales

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by ranald » Fri Jan 10, 2020 11:59 am

Hi Beat, Here is a photograph of mine. It's a 15/18 but I think very similar to your engine.
8 (32).JPG
Incidentally, if your filter housing is the same, it will have a bypass arrangement whereby if the filter becomes clogged, oil will bypass the filter and still get into the engine. It goes without saying, regular oil and filter changes are advisable. Also, take care to ensure you have the correct oil filter.
Good luck, Ranald

Beat Weibel
Posts: 150
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by Beat Weibel » Sat Jan 11, 2020 11:44 am

Thanks Ranald for the picture. Looks like a neat solution.

Chris_R
Posts: 477
Joined: Wed Feb 10, 2016 12:48 pm
Location: Twickenham

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by Chris_R » Sat Jan 11, 2020 1:13 pm

Oil pressure is of course merely the resistance to oil flow. In an engine that resistance mainly comes from the bearings on the crankshaft.
Oil thins as it gets hot and so it will flow more easily. The single most important thing in lubricating a crankshaft is the flow of the oil into the bearings. If there is a positive pressure it means the pump is trying to push more in than is leaking out from the sides of the bearings. If the leaking of oil from the sides of the bearings exceeds the capacity of the pump to supply enough then the bearings will be starved of oil and metal to metal contact will occur with obvious consequences.
Oil thickness is measured in a unit called centistokes, abbreviated to cSt. It doesn't matter really what one of those is, consider it simply a measure.
At 20c a 20W-50 will have a viscosity of around 580cSt. At 90c it will have a viscosity of around 25cSt.
At 20c a 10W-30 will be around 195cSt and at 90c it will be around 13cSt.
When you start your engine at cold you can see the viscosity ratings and consequently the high resistance to flow which you will always see as a higher oil pressure on a cold engine. As it warms the viscosity falls away quite rapidly and the flow becomes easier and so the resistance is less and you see a lower pressure reading.
An oil in a hot engine with a viscosity of 25cSt will show a higher pressure than an oil with a viscosity of 13cSt because there is a greater resistance to the oil flowing. You will not get any more oil into the bearings with the higher pressure, the bearing clearance remains the same and only a fixed amount of oil can fit into that clearance.
An oil with viscosity 13cSt might flow through the bearings a bit more quickly as the thinner oil will leak more readily from the sides. This can be a good thing because of the other function of the oil in the bearings which is to take heat away. The faster the flow through the bearing the better the heat removal.
Daimler engines were originally designed for an SAE30 oil so the design bearing clearance will be for an oil of around 13cSt at 90c.

Beat Weibel
Posts: 150
Joined: Sat Feb 27, 2016 4:13 pm
Location: Munich

Re: Daimler LQ 3-24, flickering oil pressure lamp

Post by Beat Weibel » Sun Jan 19, 2020 4:39 pm

Hi Ranald
My filter looks a bit differently.
BR
Beat
Oil filter Daimler LQ 3-20 (24)
Oil filter Daimler LQ 3-20 (24)

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