Mk4 Coolant tank and sensor

[Ant1981]

Now, I know that issues with the sensor have been covered in the past, but I want to dig a little deeper here.

I've been having the issues on a cold morning, where the dash says 'Stop, check coolant' and from this forum, I am aware that this is an issue with the sensor in the expansion tank. I've bought a new tank as I understand and can see that replacement of the sensor alone is not possible.

But, how does two 'prongs' constitute a 'sensor'? Sure, there's a plug on the other end, but does replacement really cure this issue?

[rubjonny]

its simple, the coolantvcompletes a circuit between the 2 pins, and switches off the bulb

[Ant1981]

So if that's all it is, then how can the two pins in the bottle fail, if that's all they are?

[rubjonny]

ah you changed the title to mk4, not 100% sure if its the same as a MK2/3 tank?  if it just has the 2 pins then I'm pretty sure it will be though, and yes if you join the pins on a mk2/3 tank it will switch off the coolant light

the 2 pins in the bottle can get all gummed up with crud, which will cause em to fail as they'll no longer pass current.  on the early mk1/2 tanks you can pop out the sensor and clean the ends, in a late MK2 onwards tank its all sealed up so this isnt possible.

[Ant1981]

I never even knew the late Mk2 had one.

Before my title said only Mk, I forgot to put which one in it lol.

[rubjonny]

yeah that plus the mk2 in ya sig I assumed it was a MK2 you were on about, should have noticed you said 'stop coolant check' 

I cant see the MK4 being any different, but you never know!

[Ant1981]

You know what, having thought about the prongs no longer conducting due to a layer build up, try this, it worked for me.

Open tank, grab a sharp flat head screw driver, shove it in the tank and scrape both prongs.

Never had the coolant warning since