Exhaust blowing noise

My exhaust is making an excessive noise – what is wrong with it?

If your exhaust is making an unusual amount of noise, then you have either fitted a loud sports exhaust, and that is how you want your exhaust to sound – or – more likely, your exhaust has a hole in it in the wrong place.

This is most likely caused by corrosion – the pipe or silencer box has rusted through, or a rubber mount has perished and the exhaust has cracked at one of the welded joints due to excessive movement during use. Exhaust gas, especially in petrol cars carries moisture, which can build-up in the exhaust system and over time, with high temperature fluctuations and condensation thrown in there, cause corrosion.

Once rust starts to spread on an exhaust it will quickly make the exhaust unsuitable and a potential MOT fail.


There is a lot of smoke coming out of my exhaust – what do I do?

Excessive smoke from your exhaust is never good, our advice is to stop the vehicle and park it in a safe place off the main road. Then call someone to recover the vehicle, if you are a member of a roadside assistance provider such as the AA, RAC or similar, then call them.

Lots of smoke is usually an engine issue, not an exhaust issue, but it will not be good for your exhaust either way, CATs and DPFs will be damaged by oil entering the exhaust from the engine and can quickly become blocked and need replacing if the problem is left to continue.

Engine issues are caused by a great many things failing including seals and ancillary equipment, however the most common cause of lots of smoke is the wrong fuel being put into the car petrol/diesel or vice versa. It’s easy done, so don’t be embarrassed, but don’t be tempted to drive to a garage or dive home, it will really damage your car and isn’t safe.

Reduced power

Reduced power / limp home mode – is it my exhaust system?

Most modern cars will limit engine speed if there is an issue, but the car is still safe to drive without causing further damage, it’s often referred to as ‘limp-home’ mode and designed to allow you to get off a busy main road and or get to a garage or home if there is a non-critical issue brewing. If you are a member of a roadside recovery service, then pull-over somewhere quiet and call them, if you are within a mile of home, then it may be sensible to head home and call then.

Emissions components such as CATs and DPFs and the associated sensors are frequent causes of limp-home mode, it means there is a problem, (usually blockage) with the unit. If it is a blocked DPF then the garage may be able to force regeneration – if you have been doing lots of short journeys in a diesel car. It can mean faulty sensors, or be a symptom of a bigger engine issue, so does need sorting out.

In all cases, your car needs attention quickly and generally the sooner you stop and call for assistance, the easier it will be to fix.

White powder

There is white powder coming out of my exhaust – should I be worried?

In a word, yes. It probably means your catalytic converter is breaking-up, while this won’t damage your car too much if you drive a short distance, it will need replacing quickly to avoid further engine issues occurring.

The Catalytic Converter (CAT) is often made of ceramic material, the whitish powder you see coming out of the exhaust means the CAT has fractured, this can be caused by a number of issues, 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. It won’t damage your car if you drive it to the garage, but it will need replacing.

Dash warning light

There is an emissions warning light flashing on my dashboard – is it my exhaust system causing a problem?

The emissions warning light being illuminated on the dashboard usually means a sensor on your exhaust system is failing, it can also mean there is an engine issue and this is causing an emissions warning. Usually it is OK to drive your car home, or to a garage – if it will still drive. Most modern cars have a ‘limp home’ mode which gives you reduced power, or it will stop the engine if the issue is more serious.

Don’t ignore the dash light, it will almost certainly end in a far more expensive repair or a safety issue if you do.

Most modern exhausts (2006 onwards is a good rule of thumb) have two sensors on them measuring the condition of the exhaust gas, if those sensors start to produce an unusual signal due to an issue with the engine or the sensor then they will illuminate on the dash.

If the sensor is the issue, then a replacement can quickly be supplied and fitted, if there is another issue the sensor is detecting the results of that issue, then that will need to be investigated and remedied.

If you see a dash light come on soon after having a new CAT or DPF fitted, take your vehicle back to the garage immediately and ask what has been fitted, you can always insist on a Klarius to be on the safe side. There are poor quality items out there and they will cause the light to illuminate soon after being fitted. Don’t stand for this.


My exhaust is rattling – is it terminal?

Rattling exhausts can be caused by a number of different issues, and will create a lot of noise during driving.

A baffle (a piece of perforated metal) or tube loose in the muffler box can lead to excessive rattling, and is usually caused by corrosion or poor manufacturing. While not a terminal issue, the resulting change in exhaust backpressure could reduce fuel economy. This is a reasonably cheap fix, requiring a new muffler and associated pipe.

Catalytic converter (CAT) or diesel particulate filter (DPF) failure can also increase rattling, as the internal ceramic strata of either device has failed. This can be caused by impacts during use or excess fuel in the emissions system. Generally, the failed device will require a full replacement to remedy the issue.

In addition, loose exhausts will rattle excessively. Perished rubber mountings or snapped brackets are typically to blame. Replacing the mountings might sometimes work, but if the exhaust has come under additional stress, it may have fractured. In this instance, the assembly will require replacement.