Can anyone help with the following symptons on my 3 yr old 2.0 GTV JTS. Noticed this morning expansion tank level was about 4 inches below the Minimum mark. Filled up and drove down the Motorway 30 miles. At the other end, lifted bonnet to find the level had gone down about 3 inches! (Absolutely no signs of leak on te drive or anywher under the car and no performance issues on the journey)
Waited for it to cool down (hour and half) then went to fill her up again. As I undid lid, pressure still quite high and noticed expansion tank level rose back to just about half an inch from where I'd filled before the trip. Never seen levels rise like this before.
I'd appreciate any ideas.