Low coolant warning light on

[labman1001]

Hi guys I'm looking for some help here ....

I started the car up this morning and when I went to reverse out the drive the red low coolant warning lit up on the dash ... I stopped and switched off the engine and lifted the bonnet to check the level and it's sitting bang on the maximum line where it always is ... I shut everything up started the car and everything's been fine.

Anyone any ideas on this, it was cold, -2 according to the display...

Petet

[RichieXR2]

The sensors in the coolant tank go bad and cause this fault, I'm not sure if it's the prongs rusting or another reason but it's a fairly common issue.

A new tank should sort it. £15 from eBay.

[KenONeill]

If it's the "visible prongs" type header, when the engine is cold, open the header tank and rub a flat blade screwdriver down the prongs. If it's the "invisible prongs" type you need a new one.

 

99.9% certain.

[booke23]

My Fabia (1.9 TDI PD so same coolant bottle setup as the 2.0 Octavia) used to do exactly the same. Only ever happened when parked facing downhill and the outside temp was below freezing. 

 

I would normally reverse park the car on my drive so it was pointing uphill. In this situation the warning would never come on so I just lived with it.  

[mikey vrs]

My mk1 octavia vrs used to do this & my mk2 octavia started to do this before i traded it,it always used to happen when the temp dropped below freezing,as already mentioned cleaning the prongs with a screwdriver usually works. 

[labman1001]

Well the bit about the car facing downhill certainly rings true as my driveway is on an ever so slight slope down .... Not helped by the front wheels usually resting in two built in groves from years of parking on the same spot .... I'll have a look at the sensor if I can see the prongs though and try cleaning them .... Thanks for all the help guys.

[booke23]

The biggest annoyance with this issue is that the warning won't reset just by driving onto level ground.......You then have to stop the engine and restart to clear the fault.  

[phoneman(ret)]

Same problem, but quite rare. My Octavia has the visible prongs, problem is they don't rust but get a coating on them which increases their resistance and makes the electronics they have gone open circuit (low water level). Giving them a scrape will cure the problem (for a while at least) another trick, if the coolant level has dropped a bit, is to add some antifreeze.

 

A thought, if the antifreeze is losing its effectiveness  would this cause the same problem ? I have used fluid level sensors in the past, seem to remember that the only way to stop this effect is to use AC, DC causes electrolytic effects.