Overheated on track - now what?

[infernosg]

Originally Posted by vex

Tongue, meet cheek.

Don't you have a RX-7 to work on?

Anyhow, started pulling the engine apart today. Only got to the intermediate iron before I decided to stop so I could clean the garage to better organize parts. Only thing I found I can't explain is pictured below:



Any explanation? Aside from that everything looks good - really good, but soaked in oil...

[RETed]

That's typical.
It's actually aluminum oxide.
It's galvanic corrosion due to having two dissimilar metals (steel side irons + aluminum rotor housings) and an electrolyte (coolant) - that's basically a battery.


-Ted

[infernosg]

Originally Posted by RETed

That's typical.
It's actually aluminum oxide.
It's galvanic corrosion due to having two dissimilar metals (steel side irons + aluminum rotor housings) and an electrolyte (coolant) - that's basically a battery.


-Ted

Gah, of course! In my search to find something I've managed to forget even the most basic material science. So what exactly should I be looking for given the circumstances? I have a couple other pictures of the rear iron and rotor housing but nothing looks out of the ordinary (to me).

[RETed]

Check the inner water jacket o-ring.
Look for discoloration or distortion.
Check the area of the side iron on both sides of the water jacket o-ring groove - look for discoloration.
The inside (toward the combustion chamber) edge area should be a uniform black - if there is a "clean" area, that could be signs of water leaking into the engine.


-Ted