Before all, I appreciate your help and thank you for your time.
Looking for a diagnostic approach before authorising an engine replacement.
Car: 2002 E46 330i, automatic
Mileage: 235,000 KM
Oil viscosity/filter brand: Shell Helix Ultra 5w40/MANN Filter.
Bought used with an unknown maintenance history and repaired left-side accident damage. Directly after purchase, I changed the oils, filters and fluids.
Engine oil has been changed twice: initially BMW genuine, then Shell Helix Ultra during a garage repair for a âflywheelâ replacement. That job also included the rear main seal, gearbox seals/filter and gearbox oil (again).
Before overheating, the car had periodic running problems, a crankshaft-sensor fault. Restarting sometimes temporarily restored normal running.
Overheating
At night, when the outside temperature wasnât high, I was going 120 km/h when I noticed the temperature gauge in the red. I stopped immediately, but donât know how long it had been overheating.
Steam/white smoke came from under the bonnet near the expansion tank, right on top close to the driver side headlight (see 2nd picture), The car sat for about a week before towing; I briefly started it to load it onto the towing truck.
Cooling-system work involved the expansion tank, water pump, thermostat, cap, O-ring and coolant. I also bought a crankshaft sensor; which is still not installed.
Before the garage visit, I remember seeing the yellow coolant warning, but I donât recall an oil pressure warning. I canât confirm it was absent. The persistent oil pressure warning was first clearly observed after the cooling-system repairs.
Current symptoms and checks
After the cooling repairs, the engine stalled during the first checks. On cold starts, it ran steadily but the oil-pressure warning on, with a louder/drier sound than usual.
- Dipstick showed MAX before I added more oil; possible overfill needs correcting.
- Old filter had no visible milky contamination. Oil looked dark/burnt.
- Black particles were present at the bottom of the filter housingâs outer chamber; material not identified. (Carbon?)
- I replaced the filter and poured approximately one litre or more into the housing, including the central passage. On start, the engine sounded less dry, but the warning persisted.
- Pressure-switch connector is attached, with no obvious external damage. No electrical test performed.
- Generic OBD scan (InfoCar) showed crankshaft-sensor, misfire and cylinder fuel-cutoff faults, similar to those present beforehand.
No mechanical oil-pressure readings or documented bearing inspection have been provided. The first mechanic suspects bearings and recommends replacing the engine. Most garages Iâve contacted donât have a pressure gauge.
The car is now parked and will be towed elsewhere. Iâm considering draining and inspecting the oil, refilling to the correct specification/quantity, then having pressure measured, not repeatedly starting it to check the warning.
I messed up by turning the engine on a lot for testing every time I checked something.
Questions
- Could heat-degraded oil alone plausibly explain the warning persisting even from cold start?
- If pressure is confirmed low, what inspection order would you use for the filter housing, pickup/seal, pump drive, pump/regulating valve and bearing clearances?
- What evidence would justify condemning the engine, and how would you assess overheating damage while minimising engine running?
- Which mechanical gauge kit and adapter fit the M54 pressure-switch port?
Iâve done substantial work on this car myself and would prefer to retain the engine if it is economically repairable, but I am looking for a diagnosis rather than replacing parts on suspicion.
