Weird issues with my mom's car...

[DarkoNova]

Need some help figuring out just what the hell is going on with my mom's car.

It's a 2002 Sonata with the 4 cylinder.

It's got around 151,000 miles. Basically, for a few months now it's been creaking and making a light thunking sound over random bumps. I looked at the maintenance records, and the last time the shocks were done was about 90,000 miles ago. So I just figured whatever, it's not much for a set of shocks. So I ordered some from Rock Auto and got new mounts at Autozone. Got them all installed and it definitely rides better and takes turns better, but it still creaks like crazy just going down the road. If I turn the wheel back and forth repeatedly, it does the same creaking sound. The creaking comes from the front, but there's also a light thunk coming from the rear when going over random bumps. It usually happens on small bumps/potholes on the freeway. There's no detectable play in the ball joints or wheel bearings, and all bushings look fine. I replaced a couple of the motor mounts around a year ago, but not the one by the firewall (not by choice, just didn't have the money at the time). I doubt that's the problem, but I'm open to suggestions. I've googled and there's a Hyundai forum where someone mentioned it was the swaybar bushings and to try lubing them with grease. If that works, then replace them. Her bushings don't even look that worn out, but I tried spraying them with some white lithium grease and it didn't help.

The other issue I've never seen before. The car takes forever to warm up, and depending on the temperature outside and how fast the car is going, the temp will actually drop drastically. Normal operating temp is just under the middle marker. We had some a pretty crazy storm here in SoCal over the weekend, and while driving to school I checked the temp on my phone. It was 39º. At that point, the temp gauge had actually dropped to just under the 1/4 marker. I'm guessing the thermostat needs to be replaced, but I've never seen the temp drop that much. I guess I'd just like some verification before draining the coolant...

Any ideas?

[DarkoNova]

I am sadface. :(

[MonzaRacer]

Replace the ball joints and outer tie rods with greaseable ones. Probably one of the joints thats supposed to never need greasing needs grease. If you replace the upper strut mount/bearing.
In the rear check for worn sway bar links. Or possibly sway bar bushings that mount at frame.

[JAG.]

Also check the strut seat mounts. If not installed properly they can bounce and rattle when you go over bumps. Just needs some tightening or maybe even flip it over. Just worth a check

[sniper]

I would replace the front sway bar end links. Lube won't do a bit of good on them. The creaking could be the sway bar mount bushings.