Topping up Coolant - Can I use tap water?

[s3londonuk]

As above, my 2001 S3 has just dipped under the Min level and I wanted to use a small amount of tap water to top up.

Is this OK?

Also, same question for a Focus 2005 TDCi!

Thanks

[CDP]

Probably best to use the correct Audi compatible coolant. If it's _just_ below min you should be able to get away with driving it to the VAG dealer, if topping up with water try a hard-water filter first.

[Nick3point2]

If it's only a small amount just use tap water, but if you have to do it regularly, as in there's a leak, alternately fill it with neat anti freeze, then water etc to keep the concentration.

[cuprabob]

I would top it up with some G12++ coolant mixed 50:50 with water. I tend to use deionised water as it's cheap and readily availble just to be safe.

G12++ costs around £8.50 for 1.5litre bottle and it's worth having a bottle for little top ups.

As said above if you find you are having to top it up frequently then you need to find out where it's going

[Mojocvh]

Hmm tempting but I'd go to haulfords and BUY the correct [ie matching]colour coolant and use that. IMO of course.

[TDIfurby]

For a small top-up just chuck water in. A dribble is not going to affect the overall dilution of water to coolant, and is a better short term option than running very low...

If you keep needing a dribble it might be time to check the radiator and other things for leaks. A 2001 car's radiator is probably reaching a point where it might start failing.

[LuS1fer]

I'd use de-ionised water as it's very cheap and doesn't have the lime deposits in it that will eventually block your radiator. A small amount probably won't do much harm though.

[morgrp]

I've always used tap water to top up and never had a problem with any car.

[va1o]

Why not just buy some, its not exactly expensive. I'd be questioning more why its got below the minimum level myself though, if you need to keep topping up then there's a leak somewhere.