A knocking noise when braking (or during less noticeable maneuvers) can be attributed to worn front suspension parts – especially control arm bushings. Other symptoms, which may or may not be present, are a noisy clattering on a bumpy road, odd steering feel/behavior at low speeds, and pulling to one side when braking.
Worn suspension parts can also be a cause of a knocking sound when braking. The “lower control arm” bushings can wear to the point of actually tearing apart, and then the whole front wheel assembly can move back and forth when you brake and accelerate. This will cause knocking when you brake and go over certain bumps.
The rod’s bushings are a likely source of a clunking noise. Worn-out shocks or struts are also common culprits here. With shocks, another thing to check for is loose or dried-out mounting bushings. A groaning noise when you turn the wheel typically means there’s a dry joint, likely at the idler or pitman arm.
Check the brake system and see if the caliper or rotor is damaged on the driver side wheel. Since the noise only occurs when decelerating to a stop, then there could be an issue with the brakes. If the noise is still there, then either there is a loose suspension part or there is a problem with the transmission.
Noise – this can be a clunking or squeaking noise. Clunking noises are caused by the worn ball joints rattling as the suspension travels up and down over the road. The squeaking noise is caused by the rubber boot that protects the grease inside the ball joint is damaged, the ball joint will start to squeak.
If you hear a knock or other odd sounds coming from below, the culprit is usually one of three parts of your system – your tie bar, ball joints or sway bar. All three of these can wear out with enough use, which could lead to some serious issues including total loss of steering control.
Bad strut sounds are usually described as a hollow clunking or banging type of sound. You’ll typically hear the noise when the vehicle is traveling over irregularities in the road. It’s also possible to get a bad strut mount sound —an audible clunking or creaking when turning the steering wheel.
Low Engine Oil A low oil level can cause engine knocking. If you get lucky, the noise may subside when you refill the engine with oil. In most cases, however, once the oil level gets low enough to create knocking, damage to internal engine components has already taken place.