Some time back, I did two posts on the apparent death, and then partial recovery, of my much loved Power Mac G5 Quad.
In A Casualty on the Front Lines I described discovering the machine one day with its fans running at full blast, and the CPU temperature meter hovering in the 80’s C. I shut it down immediately, assumed rather too quickly that it was done for and deduced that there was no course left but to harvest all the valuable parts I could from it and put the carcass out to pasture.
In The Reports of My Demise Are Greatly Exaggerated, urged on by reader Ty (author of the now defunct Resto-Bytes blog) to not give up without a fight, I made an initial effort to find and repair the cause of the problem, which at the time I assumed to be a failure of the G5 Quad’s infamous Liquid Cooling System (LCS). Instead, what I found was dust, and lots of it, obstructing free airflow into the CPU area of the machine.
This aligned perfectly with the blistering CPU temperatures and the full speed fan rotations and so I carefully cleared all the dust out and closed the machine back up, confident that it would now be back in the land of the living. I was wrong. It improved, but the CPU temperature stabilized in the low 60’s C region, and the fan rotations at their full value of 3600 RPM. This was both too hot and too noisy to allow me to return the G5 to full service.
Clearly I needed to get into the CPU area and get at a presumed accumulation of dust there before I could restore fully normal operation. The machine wasn’t dead anymore, but it was far from healthy.
I downloaded the G5 Quad service manual from the web and reviewed what needed to be done. It did not look like a trivial undertaking and I did not have the time just then to do anything more complex. So, I backed up the G5 Quad, restored it onto my similar vintage G5 Dual and put that machine back on line (the G5 serves as the Happy Macs Lab online Gopher server, and so it plays an important role, requiring a stable and reliable machine).
This remained the state of affairs for the next many months. Finally, I recently had the time to undertake that next step and see if I could recover the G5 Quad back to full functionality. With all of this as preamble, this post details the steps taken and the results achieved.
I started by opening the G5 Quad’s side access panel and removing the clear plastic air deflector. Anyone who has ever looked inside a late 2005 G5 will be familiar with these steps. Next, I extracted the front inlet fan assembly, which can be directly lifted out of the case with only a light amount of force. Now I had unobstructed access to the CPU area.
The CPUs and their all-important LCS are protected by a metal panel with the iconic “G5” lettering emblazoned on it. Apple calls this the Heatsink Cover.
To get at the CPU area, this cover has to be removed. This sounded simple enough in the service manual. All that was required was to locate the plastic rivet that secured the cover to the PCI divider plate directly above it, pry up the rivet’s center post and then pry up the rivet itself. With this done, the entire rivet could be extracted. With the rivet out of the way, the heatsink cover could then be removed by sliding it forward and lifting it up and out. Like all too many things however, this turned out to be quite a bit more difficult to do than to say.
I found the locking rivet easily enough. It is located at the top right of the CPU area, along the flat top surface, and was such a good color match with the rest of the panel that you almost wouldn’t notice it if you weren’t specifically looking for it. Aesthetics were everything for the Apple of 2005!
Per the service manual, I used a long handled Xacto knife to gently pry up the rivet’s center plug. This took multiple efforts and a little finesse, but in the end it was a fairly simple operation. The outer casing of the rivet itself was another matter entirely. While I managed to pry it up from the surrounding plate with some effort, I could not get it to come up far enough to extract it. Any part of it that I touched with the tips of a small pair of pliers would just come apart. Ultimately, the remains of the rivet simply fell into the housing, solving my immediate problem. The service manual did note that the rivet needed to be replaced during reassembly, which was clearly going to be a problem now, but hey, one step at a time.
With the rivet now out of the way, I was able to slide the Heat Sink Cover forward and then lift it out, leaving me with unobstructed access to the inside the CPU area. Regrettably, the hoped for accumulation of dust was nowhere to be found, and with it, any simple explanation for the overheating I was observing. I checked the LCS itself carefully, but there were no signs of leakage from it, and no obvious external damage. Since the LCS appeared to be in an excellent condition, it was probably not the culprit I was looking for.
Then I noticed a small pile of black debris lying right along the front edge of the fan inlet area.
Where had that come from? Well, there is what appears to be a thin insulating mat running along the bottom of the processor area and parts of it seemed to have disintegrated over time. The small pile of black debris appeared to be from that source. Now all that debris was sitting quietly in a tidy little pile with the machine turned off and opened up, but when it was closed and operating, this set of debris was in all probability plastered all over the inlet or exhaust areas, held in place by fan air pressure. This would very effectively obstruct airflow. Had I found a possible villain? I thought so.
I used two long handled screwdrivers as opposing clamp pieces to gently pick up and remove the debris. I got most of the large pieces out this way, but far too many times, the pieces had a tendency to come apart as they were being lifted out and then fall back into the CPU area in a shower of smaller pieces. The material had a very fine consistency, almost like dust in some cases, making it very hard to get a grip on any one piece without simply breaking up that piece. Regrettably, any physical contact with the insulating mat itself caused more pieces of debris to fall off, and as a result, it became almost impossible to get all of the debris out.
Ultimately, I resorted to a vacuum with a long thin nozzle attachment and gently vacuumed the area out, avoiding as much contact with the insulating mat as I could. While I had a vacuum engaged, I also re-vacuumed the fan filters at the front and back of the CPU area. When I was done, despite my best efforts to avoid contact with the insulating mat, there was a significant chunk of it now missing.
Other than that, all looked well, and certainly much better than it had when I first opened the G5 Quad up. Time to sew the patient up and see if this was a cure! I replaced the processor Heat Sink Cover, albeit without the now broken rivet, put back the clear plastic air deflector and finally closed up the side access panel. I reattached all the relevant cables and hopefully pressed the front power button. There was no startup chime, but nonetheless the machine fired up and quickly came to the Tiger desktop.
I am happy to report that the net result was something approaching complete success! After boot up, the CPU temperature started displaying at 53C, but then much to my distress quickly shot up to 63C. Just as I was about to declare defeat, it started to come back down. After ten minutes, the G5 was idling at about 51C with the CPU fan speed being reported as 1310 RPM. This was a HUGE improvement over my last effort, where the results had been mid 60s and 3600 RPMs.
In order to decide what “success” actually looked like, I decided to check my original install logs and see if I had taken any temperature and fan readings from the G5 when I first got it. Sure enough I had, with iStat Pro used as the source. Immediately after I installed Tiger on the G5 in 2011, iStat Pro reported 50C to 51C as the idling CPU operating temperature, and 1250 RPM as the CPU fan speed needed to maintain it. So, eight years and a little repair work later, it was once again 50C to 51C, but the CPU fans were working a little harder to keep it that way. Not a LOT harder, but a little harder… running 4.8% faster. It would seem that “success” had been achieved after all! Not bad for a 15 year old machine that I was about to strip and put out to pasture!
What can I say except” Welcome back to the real world, G5 Quad!”, and thanks to reader Ty for encouraging me to soldier on. A fine old machine is back on its feet again as a result.
Looking forward, I keep promising to report on the work I did with another now much loved machine, my Macintosh IIfx. In the interim however, I have diverted to Snow Leopard, to networking older Macs and now to the rescue of this G5 Quad, but I have not lost my thread. There is one more short post coming on Snow Leopard, and then we will return to the Macintosh IIfx theme. Stay tuned.