Just going through my service history and hadn't noticed this before. On the first variable service that was logged a fault was recorded by the first owner (me being the 2nd) describing the "coolant light on after starting from cold. switch ignition on/off & light goes out"....... with the solution being an expansion bottle required for the coolant light fault!!

Interestingly there wasn't any charge suggesting it was done in warranty?

Anyone seen had similar? Anyone know why an expansion bottle would resolve what appears to be a sensor issue?

Yep, the sensor is built into the bottle.

Yep, the sensor is built into the bottle.

Why would it be an expansion bottle though? Or is that just how they term the usual bottles?

Because its for your coolant and the sensors bugger up so you change the bottle to fix it.

.... i understand that fatty, expansion just makes it sound like a larger bottle has been fitted that's all.

.... i understand that fatty, expansion just makes it sound like a larger bottle has been fitted that's all.

Does it....lol

It sounds more like a bottle for catching water that is going through a system which heats the water thus expanding it too me. Hence the name expansion tank. Your central heating has one as well because the water get hot and expands.

Edit.....Expansion tank - Wikipedia, the free encyclopedia

HTH

It's just the name given to the standard coolant tank.

I get the same problem only when starting up first thing in the am - if I switch it off right away and restart it goes away. The level is just above 'min'....

I found a post on here that says to scrape two metal prongs located just under the cap - couldn't find any....

The sensor is built into the expantion tank & can't be removed, hence the need for a new tank. I had this problem & just changed the tank, its easy & cheap enough to do. Some people I think have cleaned the prongs & that has cured it for a while.

After taking off the cap I couldn't see the prongs - any idea where they are located?

After taking off the cap I couldn't see the prongs - any idea where they are located?

A- Shows the prongs & B- Is where the sensor is located.

Thanks Oggy - will give them a bit of a clean-up and see if that helps...

my y reg octavia thermostat warning light comes on whenever i start car when its 4 degrees C or lower when i start car but doesnt if you restart the car. form what ive heard its a common fault so im not going to go through the expense of replacing my expansion bottle when its really not needed