my heater core/matrix is leaking and i was woundering if its a big job to replace?
do all the seats and dash have to come out?
i have put some sealant in try and cure it but now its stopped hot water flowing through the matrix! is there an electric valve that controls the hot water from the the engine to the matrix/core?

any help much appreicaited. the car is a 2002 model saloon.