Why Is My Muffler Rattling – A small, discreet rattling or slamming noise comes to your ears when you ride with your dear and tender self? There are many causes of this phenomenon, so let’s try to summarize them here.
If the noise changes at the rhythm of the engine speed, it is of course that the worries are related to one of its components:
A problem at the valve level (when they take the game) of exhaust or intake usually causes an audible rattle. A hydraulic pusher can also be the cause (related to valves)
On a petrol engine requiring a controlled ignition (a candle that ignites the air/fuel mixture, unlike diesel), the rattling may come from a bad timing of ignition (in this case the distributor who decides which candle should light at this time): The candle does not “trigger” (spark) so not exactly at the right time, which causes an abnormal combustion (which may even occur when the exhaust valve begins to open!) What makes the thing much more audible)
Similarly, a dissolved injection pump (advance or delay) will not inject the fuel at the right time, which may result in the onset of rattling
One or more faulty injectors may be the cause of rattling.
Bad combustion in the engine can also cause rattling. The inflammation of the mixture is then not done in a proper and gradual way. Among the causes is a fuel that is not suitable (eg: you use unleaded 95 instead of the unleaded 98 that is intended for your engine) or an air/fuel mixture that is too unbalanced (air intake or fuel that does not arrive properly). A bad volumetric ratio (it is the rate of compression of the air + fuel in the combustion chamber at the moment when the piston is at the top: TDC for Dead Point High) can also be the cause of this kind of worries.
Too high an intake temperature (e.g. summer during heat waves) that causes too much combustion temperature (it can also be caused by unsuitable candles which also cause too much temperature in the combustion chamber). Any element that gives rise to this overheating can then be guilty of the rattling you hear, for example the malfunction of the intercooler of your turbo (which cools the air).
Excessively compressed gases sent by the turbo can trigger the ignition of the fuel too early (before the spark plug is lit), which then emits a rattle
A concern about the oil pump (which becomes noisy or does not circulate enough oil in the lubrication circuit) can possibly be the cause
A significant lack of oil can be responsible, as is the use of an oil not compatible with the manufacturer’s recommendations
As Sunadokey pointed out in his commentary at the bottom of the page, the cause may also come from weary Bielle pads. The engine case is no longer far away!
Attention, rattling can be a sign of something serious for the health of your engine, so it is essential to quickly make a diagnosis if the latter are lost in time.