Exhaust blowing noise

Exhaust blowing noise

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

• Excessive noise can be a sign there is a fault somewhere in the system

• Rattling can suggest failed exhaust mountings

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.


Holes in an exhaust are likely caused by corrosion – either 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. Furthermore, salt or chemicals picked up during prolonged road use can further contribute to the problem.

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

Exhaust Mountings

Perished mountings or snapped brackets can cause an exhaust to hang loose on the underside of your vehicle, which can result in an exhaust rattle sound that is audible even inside the cabin. This noise can become especially loud when under acceleration.

Mountings can fail due to fatigue encountered in road use, salt and associated corrosion from the roads or via an impact, for example hitting a speed bump at excessive speed. An exhaust that is not secured properly will also experience increased fatigue via excessive vibration, which can result in a premature failure.

In this case, new mountings will need to be installed to hold the exhaust in place properly. Otherwise, the exhaust could fall off during use, which will usually lead to replacement. This situation can also present a hazard to other road users. In addition, an unsecured exhaust can leak excessive gases into the atmosphere, which can place a vehicle at risk of failure during the MOT test.