I have a Honda Civic 99’ and it makes a sound like a spring that has been coiled and then let go when I go over speed bumps. Any ideas? How serious is this? Thanks for you help!
You need to have a competent mechanic check the suspension for damaged and/or worn components. This is a potential safety hazard if front-end components are in need of replacement. If you are very lucky, the noise may turn out to be merely a loose exhaust pipe, but only putting the car on a lift will tell the story of exactly what the problem is.
I agree with VDCdriver that a lift is how to find it. This could be anything from a simple loose clamp on the exhaust to a blown shock that rattles. Take it in and let them look at it, if it is suspension get it fixed right away. Good Luck!
Make mine another vote for the rack. This could be nothing serious, could be any of the already suggested things, or could even be a broken coil spring. You have struts, so if it is it’ll be part of the strut assembly, but it is a possibility.