I have this used HKS Hipermax LS+ coilover kit and It's been used about for 30000 miles.

As I drive this I actually don't hear any cracking sound or rattling from the coilover.

but some people and some articles on the internet I see they recommend the coilover need to be overhauled or rebuilt every some miles...is this necessary or not?

one of my friend told me I don't actually have to do it at all unless they are shot or the damper is not working properly.

But how can I check if they need to be overhauled? from sound?

I just can't figure out if this is working properly or not from my driving experience because this is my first time using coilover...

please tell me the method that I can do myself to check my coilover to see if it need to be overhauled or not

 

Just read your other thread, it sounds like they're blown to me.

30k is quite a few miles for coils, I asked in the other thread but I'll ask again. Did you buy these used or new? If you've owned them since new have you always kept the dampening maxed out?

Best way to find out is to pull the suspension out and compress the struts (without the springs over them) They should be pretty tough to compress with your hands and once comrpessed they should slowly expand back to the extended size. If they are really easy to compress and don't pop back to normal size then they are definitely blown and are due for a rebuild.

 

Thank you! I'll check them out.

I bought these used...that's why I'm so concerned

 

I recommended you didn't buy these coils in another one of your threads and this is why. GL with the repairs.