I still have the old matrix from my Vitesse mk2 , it’s probably the original and dated 69 . I’ve filled the matrix with 50/50 malt vinager and boiling water . The matrix took 250ml of the mixture . The matrix had a lot of unremovable crud at the opposite end to the pipes and rattled when shook . Currently the matrix is warm throughout suggesting there are no blockages or leaks I’ll leave the mixture in for 3 days and report back with my findings
Paul