Cap and Rotor Corrosion

[feerocknok]

What would cause this?

It's on a '99 XJ that my friend bought a month ago. He decided to change the cap and rotor, and that is what he found, minus the metal tab that I believe fell out as he was pulling it. It still ran...

[feerocknok]

Forgot to mention that that was after we used the compressor to blow out the thick layer of yellow powder coating everything under the outside of the cap.

[JeepcoMJ]

extreme heat and lots of moisture...have him go over the electronics, and change ALL fluids...check for water in anything, I'd bet he sunk it.

[JeepcoMJ]

by sunk I mean had it in water to that height...not literally sunk.

[feerocknok]

We already changed the oil and it looked fine, but I'll check the tranny fluid with him on Sunday.

The guy he bought it from had gotten it a year ago and the weekend he got it, he lifted it 3", but claims to have never offroaded it. He lifted it because he felt that 3" was what they should have looked like from the factory. I trusted him when he said this as he was a 52 yr old man, but accidents happen.