A sealing device for an exhaust manifold in a vehicle having longitudinally overlapping first and second components separated by a gap includes a plurality of backing rings for positioning in the gap between the first and second components. An intumescent mat is positioned between and abuts the backing rings. A retainer connected to the first and second components covers the gap to prevent the backing rings and mat from exiting the gap while allowing for relative longitudinal and rotational movement between the first and second components.