Can anyone shed a little light on this for me. I have a mk4 golf tdi for my Daily drive to work however recently the coolant symbol flashed up. I topped the coolant up a little but about 2000 miles later it once again flashes up. It does go out once the engine temp rises I assume where the coolant warms up and expands causing the level to rise. Now I'm getting no water in my oil or oil in my water so I'm sure my head gasket is fine. The car drives perfectly and always sits at 90 degrees regardless of outside temp. Also when I unscrew the header tank car it's hisses as the pressure is released and the level once again increases although maybe a fraction less than it had after top up. Any ideas??? Thanks sam

Not wishing to be the bearer of bad news but these were the exact symptoms my Bora TDI (same car ultimately) was exhibiting - except mine was pushing a header tank worth of water out of the overflow every 50-75 miles! This turned out to be a failed head gasket which I replaced. Mine would pressurise the header tank from cold after driving up to the end of the road.

I have a housemate whose parents have the same car as you and has done the same for years - same symptoms again but like yours longer between topping it up. If you can put up with it then I'd just leave it!

[Edited on 2/8/11 by andylancaster3000]

Sounds like air trapped somewhere in the system, also probable you have a small leak, under full working pressure and temperature coolant leaking through a small leak will flash straight off into saturated steam (which is to all intents and purposes in invisible).

Probably weeping a bit of fluid from the plastic housing on the g/box end of the cylinder head after use when standing which gradually lowers the level and brings the light on. My wifes one had the same problem.

[Edited on 2/8/11 by CRAIGR]

Yeh just been looking on the vw forums and it sounds like a bit of trapped air, I'm really hoping it's not head gasket!!! It sits on the motorway all day everyday so has a pretty easy life. I think I need to dump the coolant and start again as I know I have topped it up with some distilled water due to not having this "special" vw coolant the vw lads talk about. Cam belt is due anyway so may do it all at once.
Cheers sam

If this is the same engine as a 2004 A3, then I have a possible explanation.

The Exhaust gas recirc system is water cooled, and these are known to leak. The water is consumed by the engine and so "disappears". We had our pressure tested and it showed up nothing, and eventually (by using google) we worked out what the problem is, that was 10k miles ago.

It is not easy to replace and costs around £200.

More details here

http://www.pistonheads.com/gassing/topic.asp?h=0&f=86&t=811831&nmt=Audi%20A3%202ltr%20TDI%20losing%20water%20-%20Help!

Cheers matt, to be honest after having a look about I'm gonna do my cam belt and water pump along with coolant and maybe treat it to a new header tank with clean sensor. After that it's getting left well alone. It can't be head gasket as it's still hissing when I unscrew the header tank cap after 2 days of not using it so I will keep an open eye and that's about it. Had enough of modern engineering lately although the gsxr engine is all up and running lovely with nice shiny new oil cooler. Just awaiting my birthday so the mrs can buy me my accusump from andy lol.

Thanks for your thoughts and opinions people once again much appreciated