Hi guys thanks for getting back to me, celicas gone I'm afraid, needed a few jobs doing on her and she was costing a fortune to run but by far the best car I've had miss that vvti so much, thanks to help on here I found out the knock was indeed the belt tensioner piston, to keep her quiet I put a jubilee clip tight around the plastic casing on the piston, worked nicely was hardly noticeable but was still there. Again thanks for your replays if I ever get another yota I'll be back on, have fun n carry on cruising