Hi Guys,

I have done a search on M103 low oil pressure with some interesting results but it didn't answer all my questions.

I bought this car in 2005 with 168 000kms (@100k miles) from an elderly couple and it had a full service history with 2 or 3 extra engine oil changes inbetween the recommended intervals.
From the start I thought oil pressure was a bit low as after cruising at 140 km/h on the freeway in hot weather and then stopping dead the oil pressure guage would bounce of zero and settle at 0,5 in D. This is on Castrol Magnatec 10W40 semi-synthetic.
The head gasket started leaking at 220 000kms and was replaced. I remember the mech said that the cyl bores had no ridging.
Sometime before head gasket replacement it developed a sticky tappet upon cold start-up - but only for a few seconds.
The car now has 278 000kms (@ 173 000mls) and still runs castrol 10w40, has never missed a service.
Cold start-ups in warm weather produce tappet noise for longer than before and oil pressure remains at zero for @ 1 to 2 or maybe even 3 secs after start-up and then shoots up to 3 bar. As soon as oil pressure reaches 3 the tappet noise quietens slightly and then disappears alltogether.
The motor then runs super quiet.
After @ 4 - 5 mins idling and @ 60deg the oil pressure would already start dropping and at that stage is sitting at 2.5. Surely that is too quick.
If I shut down the engine and pull the dipstick the oil is barely body temp.
My plan of action for the next service is to have the oil pressure sender replaced.
What can I do about the pressure relief valve?
The delay in oil pressure after cold start-up has me worried about a bad oil pump/blocked screen?
Hot oil pressure is @ 1.1 bar at 750rpms.
I've noticed that, even with the motor idling smoothly, the oil pressure would fluctuate up and down by @ 0.2bar. I've always thought it was something electrical, but I understand the bearings cause this.
Oil pressure is quick to max out when I step on the gas.
It burns a quart of oil every 10 000kms.

Any ideas appreciated.

__________________
Free State
South Africa

What oil filter are you using??
Many aftermarker filters do not have the same type check valve that is required for
a filter mounted upside down.

__________________
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Retired Moderator

It should be OEM, as the German specialist who's been servicing it since I got it only uses OEM parts - that's what he said in the beginning and I believe him as the air filter is OEM and the oil filter I pulled out my 500 SE (also last serviced by him) was also OEM.

__________________
Free State
South Africa

According to your Mercedes Owner's Manual there is no problem here.

My main concern is the lack of oil pressure for @ 3 seconds after cold start-up and the tappet clatter that goes along with it.
Does the owner's manual state that to be normal?
Do YOU think that's normal?

__________________
Free State
South Africa

Mercedes does make a filter for that engine. I priced them a few weeks ago. They are like 28.50 each. Bosch & Mann make filters for them, as well. I am not convinced they are OEM, but possibly just made to Mercedes' specifications. On the lifter noise it should not happen on hydraulic's. However, it can an does happen. Especially, in cooler weather, and with a motor, that has milage build-up. Also, the oil that is in it has a factor to do with it. If it is not in the perscribed range in the manual for the engine, and ambient temperatures. Your oil pressure gauge should jump right up on start-up very quickly. The only other slow rising of the pressure should be after an oil change.

I have run my 1993 190E 2.6 for the past 30,000 miles using Walmart 10w-30 engine oil. Oil changes are every 3,000 miles with 1 quart of Marvel Mystery Oil installed at each change. For whatever reason my cold start lifter noises have disappeared. And Wix oil filters have given me excellent inexpensive service and have the proper valving.

My little Mercedes operates just fine in Nevada's hot and cold temperature extremes on conventional 10w-30 oil. I am more interested in oil flowing through the engine than I am with oil viscosity. I realize that 10w-30 is not a recommended viscosity in the owner's manual but oils have changed a lot since the owner's manual was written.

In no way am I suggesting that you do what I do. I'm just reporting the results of my maintennce.

I probably shouldn't mention that a few drops of MMO in the end of the speedometer cable really settles the speedometer needle down on cold mornings.

No one has ever proven that MMO really helps anything. But no one has ever proven that it hurts anything either.

WIX filters, WIX oil filters, WIX air filters, WIX fuel filters, WIX Heavy Duty Oil Filters : Filter Look-Up

Interesting engine oil article below.
FerrariChat.com - FAQ: Motor Oil Articles by Dr. Ali E. Haas (AEHaas)

Oil filter. In a pinch I've used NAPA Gold (Wix) filters, and they do this on my 300E, about 2 seconds of tappet noise on cold startup. When I use a Mann/Bosch filter, no such problems.

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1991 300E - 212K and rising fast...