3.0V6,MY05.

Had to change the header tank as small leak from cracked plastic was getting worse. Everything went according to plan and bled system as per workshop manual. Heater functions well, no leaks, temperature gauge reading exactly as before, BUT coolant level warning light comes on after driving 1/2mile and stays on until 2-5 seconds after car is stopped and left at idle. Same issue can be replicated by revving the engine over 1500 while stationary. Then I can see the coolant level in the centre compartment of the headertank dropping as the revs rise, warning comes on, back to idle, level rises and light goes off. Coolant level when cold remains the same now, no need to top up (filled to MAX when cold).

Have swapped the new sensor with the old one, re-bled the system a couple of times and gone for a 10 mile drive stopping every couple of miles to check that the light still goes off at idle. Took revs up to 4000 at times holding in a lower gear to see if there was an airlock. Problem has not improved, let alone disappeared and now I am completely out of ideas as to what to try next.

Any assistance would be much appreciated

Geoff

 

You've seen the coolant level drop with rising revs so this is a genuine 'low level' indication and not a faulty sensor / damaged harness.

Provided bleeding has been carried out effectively, I'd start thinking of a possible sticking thermostat.

Graham

 

Thanks for the response. Bleeding a further 3 times, each time going for a run to get it fully up to temperature has eventually solved the problem and the low coolant light is no longer coming on. I think that makes 6 or 7 full bleed cycles I had to go through. On an older car without the electronic wizardry, I would simply have filled up driven off and just checked the level at the end of the day. Sometimes I wonder about almost having the car tell me too much. Geoff

 

It's not the electronics. You just had an air lock. Would be bad on any car but you'd have no warning so would just do damage!