My exhaust is rattling – is it terminal?

Rattling exhausts are usually due to one of the three following issues:

Muffler Rattling

There is a baffle (a piece of perforated metal) or tube loose in the muffler box, this is usually a result of poor manufacturing or corrosion inside the exhaust. While it isn’t life threatening, it will mean that your engine isn’t working against the correct backpressure in the exhaust, which will mean your fuel economy will go down. The excess noise can be an issue if it is really loud, but is more likely just an irritation. It is a reasonably cheap fix to replace the muffler box and the associated pipe. This will help come MOT time and improve the fuel economy of your car.

Catalytic Converter or Diesel Particulate Filter Failure

The Catalytic Converter (CAT) or Diesel Particulate Filter (DPF), which are often made of ceramic material has fractured.

This can be caused by a number of issues, such as a large amount of cold water hitting a hot CAT, or a fire caused by oil or excess fuel being expelled from the engine (which is also symptomatic of an engine issue) but usually it is an impact that has caused the ceramic brick to break-up. Anything from stones to speed calming humps can do this.

Such an issue is going to affect the fuel economy of the car and also emissions levels - if it is a small piece that has broken-off then it isn’t very serious and the CAT or DPF will continue to function for a while. What is more common is the brick starts to break-up which is then more of an issue and will need replacing.

CATs and DPFs are unfortunately quite expensive, just because of the materials involved. Don’t however be tempted by a very cheap replacement, they are usually too good to be true and will lead to other engine issues very soon afterwards. Inferior CATs and DPFs will offer a reduced service life, increasing the frequency of service intervals.

Klarius CATs and DPFs are very good Quality, come with a guarantee and are reasonably priced, so if you call an Accredited Klarius repair garage you know it will be taken care of correctly.

Loose Exhaust

A loud rattling noise from the exhaust probably means it is loose and bouncing off the road underneath the car. One of the rubber mounts (hangers) or metal brackets have perished or snapped and come off from the exhaust system. This can happen with time and also when they are positioned too close to hot exhaust parts.

If you take it straight to the garage it can sometimes be possible to replace the mounting and save the exhaust system, but 9 times out of 10 it means the exhaust has broken somewhere on a joint and will need replacing. If you are lucky it will be the rear section of the exhaust that does not include a relatively costly CAT or DPF and just the rear pipe and muffler box can be replaced.