On the majority of vehicles the exhaust system is made up of several sections. It is rare that the whole system will require replacement. Technicians will carry out a free exhaust check with the promise that no unnecessary work be undertaken.
How to check the exhaust system
Scrape the surface rust from corroded areas of the exhaust and look for small holes. These may not cause a noise problem, but when the engine is on overrun, air can be drawn into the exhaust system through these pinholes and may ignite unburnt fuel passing through the exhaust. This will sound like a backfire as the fuel explodes – A backfire in your exhaust can be powerful enough to split a silencer open from the inside.
Gas leakage from exhaust joints and pipe connections will usually be marked by a streak of black soot. Any gas leaks will need quick attention because fumes can be sucked into the vehicle through vents or open windows, which could cause the driver and passengers to become drowsy or ill during a long journey. Leaking pipe connections may only need their clamps tightening or replacing.