I just had a few housings vapor blasted to clean them up and noticed a few strange looking marks on the tops of the housings. I'm up in Canada and two of the three cleaned housings came from the states, one is from my 93 Canadian FD. I have another uncleaned housing from my FD as well and it has similar areas under all the crud. While these look superficial and dont impact the housing itself (no problems with the o-ring sealing surface or damage into the coolant passages) I'd be interested to know if this was ever explained or looked into. I'm guessing casting imperfections were touched up at the foundry / factory to get more housings into cars and out the door. Because the housings are from two different countries, and thousands of miles apart, I'm almost sure these are not repairs done somewhere along the line, as I have never really heard of housings failing in any way like this.

edit - vapor blasting is pretty much the prettiest way to get an aluminum part cleaned up and have a great luster that doesnt hold onto dirt or grease like sandblasting does. Pretty reasonably priced as well - it only cost $90 to have three housings done!

 

I've seen stuff similar to that. I think it was some sort of touch-up done by the foundry.

If the water passages look good and you don't see signs that someone did something weird and tried to cover it up you're OK.

Dale