Coolant warning

[rd1]

Hi Guys,
I have looked through he threads on this and acted on the advice but still have a couple of questions that I hope you can help with.

The coolant light on our 54 A3 sportback with 40k miles comes on every now and again.

The car runs like a dream with no overheating and no apparent coolant loss. We had a cam belt change and new water pump at 38k due to the age ( no problems with the car or the coolant warning at that time though).

I have since changed the expansion tank and topped up to the max mark as the forum suggests but still have the problem. My instincts tell me its still electrical but any other ideas and
a)is it possible that there could be a problem from the water pump change?
b) given the expansion tank change,does the fault clear automatically or does it have to be reset by the dealer to clear?
Any help would be appreciated.

Thanks
Roger

[Crasher]

If the water level has not dropped when the light comes on, the car does not apparently over heat and the bottle is new you are left with a wiring or instrument fault, the latter being a known but not common problem.

[rd1]

Thought an update might help others with this problem, over the last few weeks the coolant level light has flickered on and off a couple of times. I got the cold car out of the garage the light came on and the fan was also on even though cold.

Took it to the dealers who diagnosed a second temp sender as faulty (part number 016825?) This is a separate sensor to the one in the expansion tank which I had already changed.

Wish i could have found this one as well as it still cost me £175 including diagnostics and fault clearing. Fingers crossed now that all is well but perhaps someone has a picture or description of where this second sensor is to help others change it if possible.

[Crasher]

There is coolant temperature sender 06A 919 501 A in the plastic water housing on the head but some versions have another in a coolant hose. These sensors are very unreliable.

[rd1]

Crasher,
I had the wrong part number but the invoice shows it to be exactly the one you put up. Hope it helps others although still not sure where to look for it on the car!
Roger