I changed my car's brake pads recently. Since then, I have been hearing a light thud every time I apply the brakes. It seems to come from the rear. It was quite soft in the beginning, but has become more obvious of late. What do you think is the cause and should I be concerned?
Since the symptom appeared immediately after the brake pads were replaced, it would be logical to focus on the brakes first.
When replacing brake pads, it is necessary to manually push the brake piston back into its pot. With some cars, this can be done by rotating the piston while in others, it may be necessary to use a bit of force or a clamp to force the piston back in.
During this operation, the piston seal could get dislodged. It may not be sufficient to cause a leak but, nonetheless, it can cause the piston to momentarily seize in the cylinder.
So every time you apply the brakes, the piston does not move immediately, but suddenly at a certain pedal pressure.
You may also want to check the rubber bushes in your rear suspension as they, when broken or worn, can also cause the thud when you brake.
Send your car back to the workshop to remove and reinstall the pads. If that does not solve the problem, have the brake calliper seals replaced. They are not costly.