Recently my Audi A4 came up with a coolant level warning. Finding all the coolant gone the AA were called and they did the sniff test and found the gasket was leaking exhaust fumes into the coolant. Anyway the gaskets been changed the heads been skimmed . The kit with the gasket also included the water pump and we also changed the thermostat and coolant expansion bottle plus gave it a new cap as I've heard they can be trouble.

All went well for about a month but alas a motorway trip too many and it's back loosing coolant roughly about a litre a day . We've since tried retightening the head bolts another quarter turn . To no luck . Does anyone please have any ideas what to try now ?