You say rattling... Do you think it might be underhood? Because you already found the most likely culprits and fixed them. I wonder about motor mounts and even intake movement. Rattling is not usually suspension. Clunks are. It is something lighter, and not really loaded with vehicle weight.

 

@donbrew The fins are at the point where they aren't really well defined, just some scaly rust at this point (sorry for the lack of better words here). My initial thought is they could be the original rotors on the car. I got the HHR a few months ago and have been slowly working through some of the issues. I drive a 120 minute round trip commute on very busy interstate and do a lot of hard braking. My thought after seeing the state of the rotors, is that they should be replaced because I want to make sure my brakes are up to par and that if they are warped at all etc... they could be causing some noise up front, and cause rotors are cheap.

@Blue_SS Thanks for the new potential culprits to check out, I will look at these points soon and see where it leads me.

 

I just noticed that when you are braking from medium speeds with the steering wheel straight ahead you can hear the front rattle/shake. However, when you start to turn the wheel while braking the sounds stop. Doesn't matter which direction you turn the wheel. Not sure if this helps to point to a clearer diagnoses at all, but thought I would go ahead and share.

@Blue_SS I checked out the motor mounts, all look age appropriate but no metal on metal contact. Intake looks pretty good as well.

 

Have a close look at that upper engine mount, look thru the oval hole under the fender in the front passenger wheelwell , if the bolt head is lower than the hole , the mount is toast.
the contact area can’t be seen , unless you remove the mount.
the serpentine belt tensioner and idler pulley can rattle in start up , indicating it is tired, the belt and tensioner should be changed as a set.

 

Kind of a late update, but I guess better than never....I was able to fix 95% of the front end rattle I was experiencing while braking by simply replacing the rotors. The rotors had seen better days, and it did the trick of getting rid of the chatter/rattle i was always hearing. Chasing the last 5% will be for another day. Thanks everyone for the help.

 

Based on post #13 I would look at hubs.