Temperature Concerns on Power Mac G5 Dual 2.5

Hi! My 4 cpu cores on my G5 Quad 2.5 run about 108-117 degrees F and the graphics controller and memory runs about 147F. I try to keep the room temp at 70F. Tom

Those temps don't look particularly high.

Do you keep the intake and exhaust vents free of dust and debris?

Hi-

From what I have seen reported here on the forum, the temperatures look pretty normal.
The hotter CPU A (upper CPU) is of interest, but not out of range.

I would verify the cleanliness of the inside of the tower.
Make sure the radiator fins are completely clean, with no obstruction.

Your biggest concern with a dual 2.5GHz machine is LCS leaks.
Check the mat on the floor of the tower, underneath the CPU assembly, to verify no LSC discharge.

I just reassembled my G5 (2004 2.5 GHz) cooling system last night and now appears to be working properly. Before the repair the fans were running full speed nearly 100% of the time - hardware tests indicated a temperature alarm condition for CPU A that prevented booting when hot. CPU A was typically running 10-15 ºC higher than CPU B. Other than the fan noise and booting problem the system was stable, never crashed. After disassembling the CPU's and heat sinks I believe the problem was the dried thermal grease between the CPU's and heat sink and/or the gunked-up copper fins of the heat sink. In addition, the o-rings had taken a set and the coolant had begun to seep out - no liquid, but visible residue around each of the heat sinks. I feel most, if not all, G5 water cooled systems (at least the 2.5 GHz models) will begin to exhibit these symptoms of failure.

What surprised me most about the repair was how easy and inexpensive is was. After reassembly the CPU temperatures were about 1.5 ºC apart, averaging 50 ºC under a light load. Note, the CPU's will never operate at the same temperature since the heats sinks are plumbed in series.

I have the Quad G5 and I want to rebuild the Cooling/Processor unit. I don't have precise instructions to do this. How did you repair yours? Do you have an Apple Manual? My 'B' CPU runs around 50-60% hotter than the A CPU. This seems wrong. Perhaps the temperature sensor is bad, but I want to fix the machine beore it's too late.
Thanks,
Doctor Ken

I did not have the Apple Service manual for my G5. I was inspired to proceed after viewing a step by step procedure on a french web site. There were lots of pictures so had a good idea of what to do. I did the bare minimum rebuild, replaced the o-rings, cleaned the heat sinks (covers, copper fins and visible internals) and flushed (with water) the system. I did not remove the tubes, pump or use a chemical flush. I thought it was quite easy and everything went well. I am not familiar with the cooling system of the quad G5, but I suspect cleaning the heat sinks (obviously, new fluid, seals and grease) may be all is that is required to reduce the CPU temperatures.

Ken, see this thread:
http://discussions.apple.com/thread.jspa?threadID=1940728&start=0&tstart=0