Had to replace the original matrix on my 2014 Octavia 46,000 miles because it was blocked. I read on a VW forum that this was caused by corrosion within the VW cooling system also that this corrosion leached silica out of the coolant hence the silica bag in the filler reservoir to prolong the life of the coolant. I replaced it with a Nissens matrix which apparently has wider veins . Does anyone know whether the silica bag is still required in the coolant reservoir, was it just the matrix that ru