A few years ago when I still had my Santa Fe, I replaced the clutch master cylinder, because pedal felt crunchy. It wasn’t leaking, but the travel wasn’t linear and there was a squeaking sound coming from somewhere near the firewall. I still have the old part, so out of curiosity, I decided to CT scan it to see what was up. Despite being a mixture of different metals and plastic, the scan turned out OK at 200 kV and 200 uA. The steel parts made some artifacts, but I was still able to isolate it pretty well. In the images below, the return-assist spring is on the lower left. It’s pretty much destroyed. The spring doesn’t bring the pedal back up alone - hydraulic pressure does most of that - but it does help keep it centered, which explains the symptoms that I was having. Neat! XCT is a pretty nice tool for finding defects hidden inside of things that you can’t easily open up. At least one automaker scans every cylinder head they cast before it goes into a car. Hopefully I won’t be needing to scan any more parts off of my cars any time soon, though!

These are the steel parts. On the bottom left is the messed up return spring. Up top are retainers for the hydraulic hoses. On the right is the rod that connects the piston the clutch pedal. The fork that hooks into the pedal is a lighter plastic part so it isn’t in this image.

 

Cut-plane view. Here we can see the piston itself as well as the hose attached two openings on the cylinder and the fork that connects to the pedal that weren’t visible above. I was surprised to see how much porosity there was in the piston molding itself, but it held up better than the spring so it durability is good enough.