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.

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Free State
South Africa