I got an S5 N/A rotor for my rebuild that has some surface rust on it. I've used a wire wheel to clean off the rotor faces, and I can see some pitting in the face. From what I've read, pitting like that can cause hot spots and detonation. I'm thinking I can use some fine grit sandpaper to smooth off the faces and that shouldn't change the compression or the balancing too much. As for all the grooves, I'm hoping I can scrape them clean using old seals.

Any specific things I should check or pay attention to?
Any advice on good ways to clean the groves out?

Thanks
Andy

 

How deep is the pitting? The bowl area of all rotors prior to S5 NA was rough cast anyway, so a little pitting won't be an issue.

It's a bit hard to see, but here are the rough cast faces of S4 NA rotors:



Yes, use old seals and carb cleaner to scrape the grooves.

 

rofl this picture ^ looks dirty...

 

The reason they appear dirty is due to the poor lighting, but most importantly, the cadmium plating on the rotors from the factory.

All those pictures you see of beautiful steel-silver rotors have one thing in common: the cadmium plating was either worn off, or more likely, dissolved off during cleaning.

I just cleaned up a set of rotors for my Cosmo build a few weeks ago and was totally dismayed that the cleaner I used (Zep Purple) totally removed the cadmium.

 

that's a bummer, new rotors are purdy.... and usually used rotors clean up really well

 

LOL i ment dirty as in....wow..i see lube in the corner...and a messy hole in the center of this picture covered in what could be spooge...

 

someone was having some fun with those rotors

 

Vaseline to hold the seals in place during assembly.

 

LOL^ Thats my story and I'm stickin to it!

 

If you have rotors that are badly caked with carbon in the side seal grooves, or perhaps a few bits of old side seal stuck in a groove you can use a putty knife such as this one I bought at Home Depot:



And grind into one of the corners to make a slope:



Slide it into the groove and push or lightly tap with a hammer where my finger is:

 

Looks like you could save a step and use a 5in1 painters tool instead^^^