Why Do Old Cars Rattle?
Car rides should be fun, but loud noises can ruin the experience. The only thing more annoying than the constant clanking of kids yelling “are we there yet?” is a constant clanking sound.
Not only is a rattle annoying, but it could also be a sign of a more serious problem. It’s important to find out what’s causing the rattle. When you detect a rattling noise, you can make an informed decision as to whether the noise is safe to tolerate at the moment or if it requires urgent repair.
Cars tend to rattle over time due to previous repairs, simple manufacturing processes, vibrations, thermal cycling, etc.
1) Loose fasteners
Vehicles are assembled from thousands of parts made from a variety of materials. The majority of vehicles are assembled using fasteners such as bolts, nuts, bolts, and screws.
While driving, vehicles are exposed to intense and continuous vibrations from the road surface, the engine, and even the audio system. Most fasteners are designed with a locking mechanism to securely connect components. Under normal circumstances, these fasteners are designed not to loosen over time.
However, there are many reasons why bolts and nuts can loosen and eventually cause rattles. Possible causes include aging, excessive vibration, excessive heat, improper torque specifications after repairs, and more.
2) Vibration
Vibration is the enemy of fasteners. With enough vibration, almost any component will come loose, even without the use of thread locking agents.
Engineers take these vibrations into account when building vehicles, but sometimes unexpected situations arise. If an engine mount is worn or a vibration damper is broken, the vibration can loosen several bolts throughout the vehicle.
3) Heat
As components heat and cool, they expand and contract at different rates depending on the material they are made of. If a component heats up too much, parts can warp or fasteners can become loose. For example, some types of thread locks can only be loosened by applying high heat.
4) Incorrect Torque Information
Torque rating or “torque rating” is the factory-specified torque used to tighten a screw when installing a component. This force is usually measured in Newton-meters (Nm) or foot-pounds (ft-lbs).
If a component is installed too loosely, the shutter locking mechanism will not be able to adequately grip the component surface. It may be together in the garage, but after driving on a bumpy road, the two components could come apart after tens of thousands of miles.
If components are installed too tightly, the yield strength of the fasteners may be exceeded. Yield strength is the force a thread can withstand before it becomes permanently deformed. Permanent deformation weakens the fastener and can cause premature failure. Overtightening can also damage the threads in the screw holes.
5) Installing interior panels
Interior panels can become warped or brittle over time. Also, repeated removal and installation can cause the fit to become looser.
Some manufacturers place a premium on fit and noise in the interior lining. Newer, higher quality vehicles have soft materials such as felt on the back of the contact points. This helps keep the wiring harness from moving.
Less expensive and older vehicles may have spared this expense and as a result may have more plastic-to-plastic or metal-to-plastic contact. These noises can be heard inside the cabin, especially on uneven terrain or when listening to loud music with heavy bass.
6) Age
After multiple disassembly and assembly processes, wear on the components between the fasteners and the mating surfaces can cause the screws to loosen. Fastener failure due to aging can also occur when one or more of the above conditions occur simultaneously over thousands of miles.
In other words, it’s a combination of heat and vibration over a long period of time.