W124 M111 oil pressure

[ShivaYash]

Hello all,

What is the 'correct' oil pressure for my car? It has covered 155k miles and generally been looked after I'd concluded, looking at the service history.

Following the last service, I have noticed that at idle the pressure drops to 2.1/2.2, once warm, and upon increasing engine revolutions, instantly zips up to MAX, the gauge reports this as 3 bar.

The oil used was Shell Helix HX7 10W-40 and a genuine MB filter. I note that last year when the oil service was carried out, the garage used 5W-30.

Thanks,

 

[television]

That sounds perfect to me and no wear there at all.

 

[ShivaYash]

That sounds perfect to me and no wear there at all.

Thanks M. I asked the question as this behaviour is new, post the service.

With best,

 

[television]

I cannot think of any engine that will idle at much more than 2.2 bar, that is in the order of 32lb. Sometimes just the tiniest difference in idle speed can change this

 

[ShivaYash]

I cannot think of any engine that will idle at much more than 2.2 bar, that is in the order of 32lb. Sometimes just the tiniest difference in idle speed can change this

Hmmm... perhaps the sensor was cleaned out during the service, I'll ask Terry next time we speak. I say this as prior to the most recent service, the oil pressure needle never dropped below MAX!

Thanks,

 

[television]

What ever your engine has a very good oil presure, the oil used this time does have a lower viscosity figure but nothing wrong with it and i use the same oil.

 

[Peter C1974]

My M111 engined W124 E220 has full 3 bar oil pressure at idle unless it's left idling in hot weather for more than 20-30 minutes, when the gauge drops down by a couple of millimetres, down to approx 2.8/2.9 bar.

My car has FSH and 90k miles on the clock. Idle speed is approx 650 rev/min.

My M102 engined W123 230E drops down to 2 bars in the same conditions.

 

[hotrodder]

Granted the table of oil pressures about half way down are for the M104 engine but the M111 isn't gonna be much different... http://www.w124performance.com/service/w124CD1/Program/Engine/104/18-0070.pdf
For the various diesel variants they just spec a min of 0.3bar at hot idle and >3.0bar at 3k rpm http://www.w124performance.com/service/w124CD1/Program/Engine/605_606/18-1250A.pdf

This is how the oil pressure gauge works http://www.w124performance.com/service/w124CD1/Program/Engine/104/18-0090.pdf personally i consider it a vague approximation compared to a 'proper' mechanical gauge and as long as it responds immediately the engine is revved and reaches its stop/max mark when the rpm rises >1000 the gauge is working properly and more useful than just an idiot light that tells you after the oil pressure has dropped way too low. If the gauge was regularly reading 1.5 or less at idle i'd check the actual oil pressure with a real gauge, more to ensure the pump is delivering the goods at higher rpm than worries about pressure at idle...
Oil temp, oil viscosity and a bunch of other stuff all have an effect on pressure [/physics] neglected oil changes can result in "good" oil pressure while the poor camshaft(s) are suffering due to coked up oil feeds for example. Especially designs that use a small dia spray bar with tiny holes drilled in it to drizzle oil over the cam lobes google vids

 

[WG M-B]

2bar at idle is excellent!
No we never clean the pressure switches V !!

 

[ShivaYash]

Thanks to all including HotRodder for the educational links. This weekend was really the first time I drove the car any sort of distance, London to Cambridge return, and it was a delight on the M11. I got stuck in a little bit of traffic around junctions 13 & 14 and hence the question re oil pressure as I noted it dropped off, and before Terry did the service, so far as I had noticed, it never dropped.

The new tyres are SO quiet and after Wheels In Motion worked their magic, the tracking is spot on.

Glad to hear this is normal and I suspect whether or not the last time a real MB filter was used ;-) but I know my good friend Terry used a genuine one as I supplied it.

Off to Oxfordshire next weekend and am looking forward to the drive.

With best wishes,
SY

 

[syncropaddy]

I've seen this in an M111 engine that was fitted with a spurious filter. I doubt if the pressure switch was tampered with ..... its in the most awkward place ever!!