Replacing an exhaust downpipe

Dave Barker shows what is involved in replacing a Discovery 3 exhaust downpipe

How to replace a Discovery 3 exhaust downpipe and catalytic convertor

AS cars have advanced over the years, the basic exhaust system has hardly changed. It may have had various sensors and catalytic converter added into the pipework, but it remains almost unchanged and is still essentially a steel pipe taking exhaust fumes from the engine to the back of the vehicle. And even when made with better materials, such as stainless steel on the Discovery 3, it can still leak exhaust fumes and need to be replaced.

In the case of this 2007 Discovery 3, the small flexible section of the front downpipe near the manifold was leaking. The movement between the exhaust downpipe and the engine had caused the flexible section of the pipe to crack. Once this happens, it needs changing as soon as possible – with the engine bay being very cramped on a Discovery, a hot exhaust gas leak could easily melt some nearby parts or electrical wiring.

The exhaust system on a TDV6 is in

two sections. The front section is a short downpipe running from the turbocharger, via the flexible section, through the catalytic converter to the much larger and longer rear section which incorporates the centre silencer and two tailpipes with silencers. So we need only replace the front section. However, as this includes the catalytic converter, it not a cheap section to replace.

Replacing the front downpipe section would not be a difficult job if carried out with the vehicle on a lift, except the exhaust manifold nuts are usually seized. If so, they will need some heat to free them, as a snapped exhaust stud will make the job much more difficult. The gearbox crossmember securing bolts may be seized and may also require a little heat to free them.

New downpipes are pricey, so for the vehicle in this feature a secondhand front downpipe was sourced and supplied by the owner of the Discovery, and handed to Maddison 4x4 to be fitted.