A few days ago I had my van with 1.9l waterboxer idle for maybe an hour or so everything was running fine when I parked it. Now tonight I started my van after a few days in the garage and it is knocking very bad. It seems like it's coming from around the valve cover.

I did check the oil and it was missing 1Litre which I did add and let the egine run and drove it for about 2 km and still knocking.

Can anyone guide a bit and explain what could have happenned so suddenly.

Thanks,

Michel Bertin