how wound i detect a leaking servo mate

i have a 200tdi which has decided too keep blowing oil dipstick out and getting different answers from garages some say head gasket and some rings and pistons anyone any ideas have lost no power or increase in water use :doh:

thanks mate

just thought id say hi to all as a new member on here hope to have hours of fun,and learn more about landys ..:o:o:o