2002 C5 2.0HDI low oil pressure ?

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2002 C5 2.0HDI low oil pressure ?

Post by 2cvandy »

I've looked through old posts and whilst I've found similar problems, I've not found a solution.
It's not urgent, and I'd be pleasantly surprised if I get an exact diagnosis and cure, because it's an odd one, but I'd be interested in your thoughts.

The car's a 2002 C5 break, 2.0HDI with 216,000 miles recorded.
The problem started a year ago, but I thought it was cured.
I'd recently done an oil / filter change when the message "oil pressure insufficient" flashed up on the display.
The car was running fine and sounded fine, so I carried on home.
Once home, I found a (very) slight oil leak from the oil pressure switch, so I replaced that and the message never reappeared, until now.
We are now a year (and 12,000 miles) on, I've just done another oil / filter change, and the "oil pressure insufficient" message is back.

At first, I thought it must be connected with the fact that the oil has just been changed, but I always use a good quality filter and always fill the filter with oil before fitting.
Then I noticed that the message is only flashing up when braking to a stop downhill, so I though maybe the fault lies with the oil level sensor rather than pressure ? I confess, I'm not sure if that's possible ? Wouldn't the message read "low oil level" if that was the case ?
The message hadn't shown for a couple of weeks, but then yesterday morning it was back. But then I realised something else, it was -6 deg yesterday, and I've only been getting this message when the engine is cold, once the oil temp gauge gets above the blue section it stops happening. I can't remember if this only happened in cold temps last time, but it was winter.

Thoughts ?