My car (Volkswagen Jetta 2008 at 90k miles) makes noise like an old mattress springs right after going over a bump. I know I can put WD-40 to see if the noise goes away but there are dozens of smaller parts (parts of all 4 different suspension assemblies) and I don't want to lose track of the culprit by putting WD-40 indiscriminately. What is an efficient way to locate the bad part?
Sorry but there are too many possibilities as to components and all need to be in working order due to safety. Car handling totally depends on suspension. Any shop can inspect and provide an estimate for free. No guessing allowed. I presume this car was not purchased new so there could be damage that needs to be corrected. Sorry. Cheers.