Hi all. I'm new to all this, so I'm not sure if this is the correct way to get a question answered. Apologies if I'm hijacking etc. My problem is the oil pressure warning light and buzzer going off. I looked at Penbryn's troubleshooting guide but hit a few snags. Here's what's occurring in more detail:- T4, engine AJT 65kW TDi, 02 reg. Problem first occurred a couple of times one day 1 month ago on a long high speed journey, red oil warning light and buzzer goes off typically around the 2000rpm mark, often when cruising down in a higher gear for a junction (but not always). Dropped a gear, increased revs, light and buzzer stop flashing and sounding. No problem for another month, during which time I have changed oil and filter (10 days ago). Two days ago, oil light/buzzer problem starts again, but requires a 30minute drive (to get oil nice and hot I presume) before it does it. Still stops once I increase engine speed, but re-occurs fairly frequently.
Following Penbryn's guide, I look for the two oil pressure sensors, but I can only find one. I'm aware he notes that later engines do not have DOP, so assume maybe this engine does only have one oil sensor. The sensor I find is a brown sensor located at the front of the crankcase, just O/S of A/C compressor, with a yellow wire. I followed the high pressure sensor test list and with yellow wire disconnected, oil light does not come on at below 1800 rpm, oil light+buzzer sound at 2000+rpm. With yellow wire grounded the light+buzzer does not sound at 2000+rpm. When I connected a light between sensor and battery, the light came on at idle speedsand stays on at higher speeds, but I now realise that the engine was not hot during that test.
Can anyone tell me, is there another oil sensor on my engine? I looked on top of the filter/cooler housing, around the cylinder head, all over the place, but there is a lot of stuff in the way to hide a sensor behind. From what I've found, the brown sensor appears to be a 0.55-0.85 bar sensor- is this correct? I note that this pressure range is in the middle of the pressures quoted by Penbryn for the low pressure (~0.3bar) and high pressure (~1.4+) sensors, so maybe having one mid-range sensor is an attempt to replace the theoretically better but temperamental DOP system with high and low pressure sensors, with a practical working single sensor. If there is only one sensor, I don't understand why oil light does not flash at low engine speeds with yellow wire disconnected.
Any suggestions? For peace of mind, my next move was to get oil pressure checked by a workshop as I do not have a pressure guage or know where to attach one, but if there are any other checks I can make before handing my wallet over, I'm listening.
Cheers