So I am working on a PowerMac G5 for a client of mine.  Initially reports were that the unit smelled like smoke/burning and that it would not turn on.  I received the unit thinking that it was a power supply issue.  I ordered the PSU and then started to disassemble it.  Lo and behold I found an entirely new issue.  This unit is liquid cooled.  This means that it does not use a regular heat sink + fan.  Instead it uses a water cooled device which is like a radiator inside of a car.

Now the problem with this is that overtime, it may spring leaks.  I am guessing that it is truly a manufacturer’s defect.  Not necessarily Apple’s fault but the fault of whoever’s heat sink design they used in the first place.

As you can see on the first three pictures, there is a lot of corrosion built up from the spilt liquid.  This is not just a PSU case.  It’s going to take a lot more.  I found several websites with a lot of detailed information.  This is definitely not an isolated occurrence.

http://www.macintouch.com/readerreports/powermacg5/topic4243.html
http://www.xlr8yourmac.com/systems/G5_coolant_leaks.html

Read to your heart’s content.