Update.
Starter installed, works great. Turbonut, not too worried about it going out again being an AutoZone product, I'll likely sell the car before that happens and if not, super easy job. Thanks for the 2 cents.
Good news is that I beleive I was able to rebuild the vacuum pump with minimal effort. Hopefully the following will help someone else save the $570 parts and labor Hyundai wanted to just remove and replace.
Funny thing is in order to change the starter, you have to remove the vacuum pump assembly. With it removed I decided to disassemble it and investigate. It's located in plain sight by the oil filter (first remove the plastic shields):
Once off the car you'll need a T-20 and T-10 torx bit to take it apart. Once inside the pump you'll see black dust everywhere. I think the spinning cylinder and flat pieces that generate the vacuum pressure is made of some type of carbon. Here's the inside:
The nice thing about whoever designed this pump is that you can't put it back together wrong. Everything fits one way. Just be careful not to loose the tiny shaft that sits below the carbon looking cylinder:
Inside you'll also find two blue seals (likely silicone). Be gentle with them when cleaning. I used isopropyl alcohol. Once apart I started to think that a leak could also be an under-perfoming pump. Either way, I wasn't too impressed with the surface finish of the sealing surfaces. You could still see the machining grooves:
I decided to wet sand all the metallic sealing surfaces starting with 1500 grit, then 2500, then 3000. Now the grooves are gone, super smooth surface. The rubber seal should need less compression to achieve a seal against the flat surfaces:
Here's all the parts minus the black plastic cap/screws:
One thing I noticed when taking the pump apart was the 4 carbon like flat pieces had a somewhat uneven worn flat on the contact surface. This may be contributing to the underperformance of the pump. I decided to flip them 180 degrees since they looked symmetric. The opposite side had a perfect radius:
Before:
After:
Everything is back together. Took the car on a test drive without any issues. Only thing I wish I did was take a vacuum reading before and after the rebuild to confirm an improvement. I will definitely give an update in a couple weeks whether or not this fixed the issue. Thanks everyone!
