Ever see anything like this?

 

Looking for ideas of what caused the power steering pump to explode om my '91 Legacy. The outiside temp was 17 deg F. The car was started and in less than a minute a "pop" and was heard followed by a hissing/fizzing sound. The car was shut off and when the hood was opened it looked like a orange julius had been poured over the engine valve cover - foamy orange color.

 

First thought would be the ps fluid froze. Never heard of that. Even if say the rack was frozen, it would seem that there are weaker points like hoses that should have failed before the thick walls of the pump.

PS fluid is usually red or white/yellow, not orange, so I think moisture is a possibility. Sometimes there are also simply bad casts, albeit very unusual, it does happen. It was probably just bad luck more than anything else. I would be careful to keep the engine warm anyway at that low a temp, because the temp diff between outside and inside the pump can cause it to crack too. (though that is unusual too)

Newer subies use ATF for the steering fluid. If yours was orange, it's hard to say what the heck was in it, or got into it for that matter.

 

Maybe condensation? You may never find out...

My dad and I figured it was due to an old stress fracture in the housing and it finally gave up. There had been times in the preceding months that the steering was tight on startup and would eventually go away. Either-who, spent the 125 at autozone for a reman pump and swapped them out, used the new pump and an electric drill to purge the rack and fill back up with ATF...works like a champ now that it has ATF and not frothy PS fluid in it.