OM366LA Oil Pressure

#1
The questions continue... Not sure if this is all right or not but our oil pressure gauge stays up at 5 bar (top of the gauge) while above 2000rpm. I had thought that maybe an oil change might change this but it is still the same. Is this what you guys are seeing? I am not used oil pressure being at the top of the scale.
 

Sitec

Adventurer
#2
The questions continue... Not sure if this is all right or not but our oil pressure gauge stays up at 5 bar (top of the gauge) while above 2000rpm. I had thought that maybe an oil change might change this but it is still the same. Is this what you guys are seeing? I am not used oil pressure being at the top of the scale.

Mine goes straight to the top of the scale when cold, and only drops off when warm.. At high revs tho it sits at the top of the gauge hot or cold. When I bought the truck, the gauge was reading really low. First thing I did was put a mechanical gauge on it to check it. Confirmed 60 PSI, so I ordered a sender from MB and fitted it. The high readings probably explain why my last sender was knackered!
 
#3
Mine is the same. Full 5 harsher cold and at 2000 revs upward.

Drops slightly when warm after about 10 km to around 4 to 4.5.

I must admit that I am not entirely sure what the oil pressure tells me but I guess when its different to the norm its saying something.

Neil
 

Sitec

Adventurer
#4
With the V6 (OM441), I've been told they have a trait where the camshaft bearings work their way out as the oil pressure starts to drop on higher km engines, and then when it suddenly drops the bearing has slid right out and oil then has no restriction resulting in a drastic drop in pressure. Not sure if its the same on the OM366's... As you say Neil. A gauge reading something is is the norm, and then when it drops question it! :)
 
#6
Thanks guys, this is my first engine that operates right at the top of the scale. A little unsettling at first as high oil pressure can be a sign of restriction in the oil system (which is why I thought maybe an oil change might change things, who knows when it was last done). Now I can stop worrying about it and just watch for any changes.
 
#7
Interestingly, yesterday i had to do a very long climb from sea level to 3000 meters. It took well over 1 hour at 20kmph at 2500 rpm.

My tempreture rose to near 100 and my oil pressure dropped to 1.5 bar. It just shows that as the oil thins it makes a big difference.

It was a good work out for the truck and she behaved perfectly

Neil
 
#8
Interestingly, yesterday i had to do a very long climb from sea level to 3000 meters. It took well over 1 hour at 20kmph at 2500 rpm.

My tempreture rose to near 100 and my oil pressure dropped to 1.5 bar. It just shows that as the oil thins it makes a big difference.

It was a good work out for the truck and she behaved perfectly

Neil
I have run that hot after the viscous fan failed. Oil pressure never dropped from 5 bar, that pressure drop does not seem right to me Neil.
FYI Mercedes allows 100 degree engine coolant temps for 10 minutes, after that you should stop and allow engine to drop to normal(at engine idle).
 
#9
I have never run that high before. The viscous fan kicked in and the tempreture held. I idled it for about 15 mins at the end and the temp dropped to normal and the pressure returned to normal. Driven anout 200km since all good. Maybe altitude effects it
 
#12
Not to derail the oil topic but as I am still trying to learn this truck the term "viscous fan" is a new one to me. So I looked it up and it is a thermostatic clutch the for the engine cooling fan. This might explain the noise we hear come and go as we were driving down the very hot interstate at speed. With a constant speed we would hear a whirring up, then the sound would stay constant, the after a few minutes "wind" down. Is this what you guys hear when your fans engage? Just trying to get used to all the "normal" sounds of this truck so we can be aware of the abnormal ones.
 
#13
Yes John, That's normal.

Out of interest, if yours is like mine you can turn a locking bolt on the back of the fan that locks it on all the time if you felt it needed it.

Now I am currently on 15w 40 mineral oil.( usually use 10w30 but you cannot get that grade in Mineral oil in Chile , which is where I am now ) Its only available in synthetic or semi synthetic which I don't use.

Yesterdays occurrence was new to me , I have never worked the truck that hard for that long. It was the longest constant uphill I have ever done. I will check my dash cam but it could have been an hour and a half with the revs at the top of the useable scale. 2300 to 2500 rpm

The truck did not mix a beat and worked brilliantly

As the truck returned back to normal almost immediately after the temperature was back down I am not concerned.

I. Think mineral oils must get thinner as they warm up. When I start my engine from cold it is always the full 5 bars pressure. After about 15km it has dropped to 4 and will normally remain at this level when driving .

It had an oil change 1000km ago so its good oil

Neil
 
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DiploStrat

Expedition Leader
#14
Altitude is a killer.

-- A turbo helps, a lot, but you are still going to run way rich.

-- I have never noticed a change in the oil pressure, but then I lived at over 3,000m and didn't go down much, so the only pressure that I saw was the reading at altitude.

-- Engines tend to run hot - watch the gauge.

Be sure to use your exhaust brake. If your 917 is like mine, there is very little engine braking without it.
 
#15
The locking bolt on the fan is there to be used if the fan clutch stops engaging. Running the fan locked will raise fuel consumption and stop the engine reaching operating temp in cold climates.
Our clutch failure was a mechanical failure between the rubber mount and cup that mounts to the engine, we were very lucky that the radiator was not damaged!
It does seem like altitude is a contributor to your pressures (Neil), we have only climbed over 10,000' a few times and those were below freezing temps. We are looking forward to the Andes!
Jon, the fan noise engagement/disengagement is normal.
 
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