I have Audi A3 2.0l fsi 2004. Yesterday coolant start leaking badly..I managed return from trip using lot of water...100km I use 6 l water! See antifreeze ander my car

. Last night can't faund any leak..today drive car around town and no leaks.. turn air to cool from 24C inside car and leak start again..

Any one have idea why and where possible leak???

Can't see any leak from above engine compartment.  Will try to remove bottom shield and check underneath 

Edited June 16, 20223 yr by Sergei

Found leak.  Any one tell me what is it? Just above oil filter on engine block..thermostat housing??Hollow Hex Plug

Hello Sergei,

Can we take it you actually added 6ltrs of coolant (antifreeze) to your coolant header tank over a 100km journey? If so then this is a major (in caps) - almost unbelievable coolant loss. The reason why using the air con affects that loss of coolant is confusing, but now that you have found a leak sight, then obviously you to fix that leak - either yourself or at garage, but certainly with urgency.

You don’t tell us what engine is in the car, but from the general description it could have been associated with the thermostat housing on certain petrol engines. From your photo - ? 
Has the car overheated at any time during this coolant leak? 
Kind regards,

Gareth. 

No overheating,  just normal temperature 

 I will try next couple days remove alternator to more space. Fingers crossed I have access and fix this leak. 

Thanks 

Engine AWX 2.0L FSI