Coolant level warning light

eekamouse

Member
Morning - took my 1.6 FSI for a 200 mile round trip over the weekend with mostly motorway miles. The car almost exclusively does short runs in town.

The morning of the second day, what I think is the coolant level warning light came on on cold start. I added some water the to the expansion tank and the light went out and the car ran perfectly on the return trip with the temp holding steady right at 90 as it always does.

I have no problems with the engine in 5 years - other than the oxygen senor issue common to the FSI.

After cooling down back at home the light came back on the next time I started it but went out after ~5 mins of running.

Any pointers here on where to get started appreciated - I realise it could be a leak (head gasket or rad) or the sensor - but if the hive mind has shares experience with this one I would appreciate it

Cheers
 

Attachments

  • coolant warning light 2.jpg
    coolant warning light 2.jpg
    952.8 KB · Views: 348
The low level sensor is in the expansion tank. The contacts can have a build up of deposits on them to give a false reading or there is a possibility the reading is low due to a coolant leak. The expansion tank cap seals fail, coolant can also leak through the level sensor and the tank itself can split. Are there any signs of leaking coolant on or around the tank? Then of coarse there is the notorious death pipe that fits between the water pump and thermostat housing. Other than those main issues you could have a leaking radiator or water pipe, cabin heater matrix leaking, head gasket problem or water pump itself leaking.
 
Last edited:
I have the same thing happening on our 1.6fsi too, only happens when it’s very cold (3 degrees or lower outside temp) no warning on warmer temperatures.

Just had a full service and inspection from WOM so I don’t think it’s a leak otherwise I hope they’d have spotted it.
 
Expansion tanks are not that expensive to replace. That way you get a new tank, new level sensor and a new cap with new seals, just go for a good quality one.
 
Expansion tanks are not that expensive to replace. That way you get a new tank, new level sensor and a new cap with new seals, just go for a good quality one.

If you can suggest an aftermarket make then it would help me too (possibly) but the last time I checked online you could only get them from VAG. You could probably get one for a different VAG model but the mounts would be different.
 
Start with the sensor in the tank. It get a lime like deposit on it, that acts as an insulator, so thinks the level is low. My TT does exactly the same at the onset of winter. First couple of years, I topped it up with concentrate. Last year I cleaned the sensor with a wire brush, the small propelling pencil type, where you get several types of brush, brass, steel, fibre glass etc. No problem this year ?
This would be suitable:
Mac.
 
Already said the sensor builds up with deposits. Wrong coolant makes it FAR worse. Just checked for availability of expansion tanks, nil stock. So assuming tank is intact cleaning of the sensor and replacing the cap / seals are about all that can be done currently unless fitting used.

In the past I have cleaned all the internal staining off the expansion tank be removing it from the car. blank off all the pipe connections using suitable bungs ( fingers cut from plastic / rubber gloves and elastic bands to hold tightly ). Grab a small handful of small stones, gravel or ball bearings ( fish tank gravel ) and pour down through the filler, add a crushed dish washer tablet and add warm water till about 1/3 full. Replace the cap and shake the expansion tank while slowly rotating it to reach all surfaces. Be careful the blanks do not come off or leak. Keep shaking the tank until all the discolouration has gone. Remove the cap and tip out the contents making sure it all comes out. Refill with clean water and after fitting the cap shake for a couple of minutes then dump the water. Repeat the rinse a couple more times. Empty and remove all the blanking and refit to the car making sure all hoses are tight. Refill with correct coolant and burp the air out by running the engine with the cap off. Refill as needed, Take the car for a 10 minute run obviously with the cap fitted to fully circulate the coolant. When you return remove the bonnet to check for leaks carefully with the engine running. Switch off and let cool before checking the level and any top up needed.
 
Last edited:
Already said the sensor builds up with deposits. Wrong coolant makes it FAR worse. Just checked for availability of expansion tanks, nil stock. So assuming tank is intact cleaning of the sensor and replacing the cap / seals are about all that can be done currently unless fitting used.
I’ve the correct coolant for sure so a good clean will suffice hopefully
 
Back
Top