As well as some other oxygen sensor faults to do with the car running too rich, we've been getting the red coolant level or temp light coming on asking us to pull over.  Happens intermittently, small trip or long. The car isn't low on coolant or showing anything but normal temp on dash gauge, (Has been to auto electrician, who have been sorting the other faults, but the coolant warning doesn't seem to be saving, they can't see anything logged.  When it has happened, after leaving for 5 mins, the car drives fine without the warning light coming back on. Anyone have any idea's or had this experience and got to bottom of it.  The car has done 170,000k's.  Has just had pretty dirty spark plugs replaced by auto electrician who was trying to sort running rich issue. 

1 hour ago, wesleysmith said:

As well as some other oxygen sensor faults to do with the car running too rich, we've been getting the red coolant level or temp light coming on asking us to pull over.  Happens intermittently, small trip or long. The car isn't low on coolant or showing anything but normal temp on dash gauge, (Has been to auto electrician, who have been sorting the other faults, but the coolant warning doesn't seem to be saving, they can't see anything logged.  When it has happened, after leaving for 5 mins, the car drives fine without the warning light coming back on. Anyone have any idea's or had this experience and got to bottom of it.  The car has done 170,000k's.  Has just had pretty dirty spark plugs replaced by auto electrician who was trying to sort running rich issue. 

OK, with the engine cold. if you open the expansion bottle, can you see a couple of metal prongs sticking into the coolant?

 

If yes, rub a fairly wide straight blade screwdriver down each one a few times. This should stop the spurious overheat warnings for a year or 3.

If no, then I'm afraid you need to replace the bottle (maybe GB£20).

It’s a little difficult but I can make out two small round prongs at the back under where the plug location is. I can’t get the photo to show them but is that what you’re talking about? Or are they more central in the model your talking about? 

Edited 17 January, 20251 yr by wesleysmith

Had the same isssue with an octavia. Low coolant sporadically but level ok. I bought another tank but never got round to fitting it and since then its cured itself. The metal prongs can get dirty/coroded and cause false singnals.

4 hours ago, wesleysmith said:

It’s a little difficult but I can make out two small round prongs at the back under where the plug location is. I can’t get the photo to show them but is that what you’re talking about? Or are they more central in the model your talking about?

It looks plausible. Can you reach them with a screwdriver? If not, a new expansion bottle was about £25 the last time I looked.