I agree that level can go down due to air in the system, but can it come
up again completely when cooling down? I would guess you would find the
level staying too low.
No recent experience though, luckily enough I haven't had cooling issues
for a long time.

Jaap,
'87 caravelle diesel

> Jaap Nauta wrote:
>> Probably bad sensor or contacts. If the needle stays in the middle,
>> temp is fine, and the red light indicates level too low. Level was OK,
>> so sensor is bad I guess.
>
> Don't overlook that, when there is air in the system, revving up the
> engine will cause the coolant in the expansion tank to go down and can
> cause the red light to flash.  Then, when you shut off the engine and go
> back to have a look, the level comes back up so it "Looks" OK.
>
> Mike