So several months ago my quad lCS started acting weird(or maybe it wasn't the LCS). CPU B was hitting 100C degrees and then the machine would shut off. What I read online was that the LSC must need more water - I looked into doing this but I thought that a conversion to air cooling would be easier and a longer term solution. I had two dual 2.0 cpu heat sinks sitting around so I made it work and got the quad cpus attatched to the 2.0 ones. Problem is CPU B is still hitting >90C while CPU A is at 40C (I tried a thermal calibration but it just says 'communication error', maybe because the LCS isn't plugged in). I opened it up and tightened everything to make sure it was making good contact and it looks like it is. So my hunch is that maybe CPU B is bad (even though i've tested it for errors). My other guess is that it could be a bad heat sink - wondering if anyone has heard of this? The heatsink I attatched to CPU B was used on a 2.0 G5 CPU that went bad. Any thoughts on this would really help, thanks.
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G5 Quad air conversion help
- Thread starter PowerHarryG4
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You could swap the CPUs to check, but I think that your CPU B is getting hotter because it is more used than CPU A. If I remember well, MacOS uses more CPU B than CPU A.
Could you share pictures of your setup? Did you use heatsinks from dual cores G5s or from older G5s? I am considering air cooling for one of my Quads and I'm looking at my options.
Could you share pictures of your setup? Did you use heatsinks from dual cores G5s or from older G5s? I am considering air cooling for one of my Quads and I'm looking at my options.
I am sort of in the same boat. Except for me, A is hotter than B. When in full power mode, A can get close to 90C or a little higher and I have to switch to reduced performance mode to cool it down because it seems close to the point of locking up. I broke it down and repasted and it took the temps down a little, maybe 5-8 degrees, but A still seems to run too hot.
Good idea, i'll swap them and see what happens. I might try swapping a heat sink too. I used heat sinks from an older G5, a DP 2.0ghz from 2005. You have to cut some of the aluminum sheets off the smaller processor heat sink to make it fit but it does fit. And if CPU A is anything to go by (maybe it is that the system is using it less) then it does effectively cool the system just fine. The only problem is mounting the CPUs to the motherboard. the screw holes are all in different locations.
My solution was to take the bracket that holds in the powercord for the CPU fan and spin it around. You can then screw four screws to mount the CPUs to that bracket and then screw in the bracket to the motherboard. It really isn't the best method but it does hold everything in place (although now you have to unplug the cable for the fan everytime you take it out).
Here's the braket I used to mount the CPUs to the board
Here's the CPU heat sinks I used from the DP 2.0 (I think it was the 2005 model). Ignore the bad writing that was me labelling a bad 2.0ghz CPU.
Update on this. I changed the heat sink on the problem CPU and it solved the issue now both CPUs sit comfortably at 30-40c idle and go up to around 60 under load. However, now I have a new problem. unscrewing the CPUs and playing around has shifted my U3 heatsink. it use to have nice cool temp and now reaches hits 80-85C under load!
@PowerHarryG4 would you be able to confirm cooler part numbers and maybe also share more photos indicating what exactly you turned and what you chopped etc... Thanks 
Got a bit of an update to this. I managed to take the whole thing apart and repaste the memory controller at the back - it's much better now (surprisingly the past wasn't dry it just wasn't making contact I suppose), it gets to about 65C and stays there under load. The CPU heatsinks were from a 2005 Powermac G5 dual 2.0 Ghz so as you'd expect they weren't made to cool a G5 quad, however i've only seen the CPUs go up to 69C under load, which I wouldn't consider too bad. Although it is a bit noisy while under load it's better than a watercooling system that doesn't work.
As for the method I used it's easier than most but it's a bit hacky and cheaty as the CPUs are only held on by four screws which is not ideal. I've taken some more pictures to show how I got it to fit. Shown below are the four points that will be screwed in (Photo credit cameron Kaiser).
This heatsink attached to the 2.5DC CPU was slightly too tall to fit on the older Heatsink - so if you cut about 5 fins it will fit. (maybe try to do it less messy than I did)
Shown below is how I too the fan socket bracket and spun that around in older to align the screw holes to the board.
When put into the computer they should line up and you can screw in those two screws.
As I said this isn't the best method and you could most likely improve this by drilling into the metal block at the bottom if you wanted to align more of the screw holes. If you're going to do this be very careful moving it and if you're traveling with it in a car for instance I'd remove the whole CPU block first.
As for the method I used it's easier than most but it's a bit hacky and cheaty as the CPUs are only held on by four screws which is not ideal. I've taken some more pictures to show how I got it to fit. Shown below are the four points that will be screwed in (Photo credit cameron Kaiser).
This heatsink attached to the 2.5DC CPU was slightly too tall to fit on the older Heatsink - so if you cut about 5 fins it will fit. (maybe try to do it less messy than I did)
Shown below is how I too the fan socket bracket and spun that around in older to align the screw holes to the board.
When put into the computer they should line up and you can screw in those two screws.
As I said this isn't the best method and you could most likely improve this by drilling into the metal block at the bottom if you wanted to align more of the screw holes. If you're going to do this be very careful moving it and if you're traveling with it in a car for instance I'd remove the whole CPU block first.
This is exactly what I did but I removed the metal frame at all (the front fan still fits nice after you connect it to the cable) and rather than cutting - I just bend the copper tubes a bit.
Yeah I just rest the Mac horizontal and when I went to vacation with it - I just removed the CPUs and put them in a bag with the pins facing up (and the bag being exactly the inches to fit both CPUs tight).
Yeah I just rest the Mac horizontal and when I went to vacation with it - I just removed the CPUs and put them in a bag with the pins facing up (and the bag being exactly the inches to fit both CPUs tight).
I'm sorry to necropost, but I'm trying a similar approach on a Quad G5 with failing LCS. Upon installing the heatsink on the CPU module, I realized that the plastic spacers are a bit too long and prevent the CPU from making contact with the heatsink. There is a gap of a few millimetres. I can tighten the four screws at each corner of the CPU to force contact, but the PCB get a little warped (I tried with a non working CPU module). Did you encounter a similar problem? If so, how did you manage? Thanks.
Yes I did have that problem. My screws for the CPUs came with spring washers on them. I removed the springs and made sure not to over tighten to screws, I just tightened until it was firm. I’m unsure how the PCB is getting warped. Can you send some pictures so I can see what you mean?
On the first picture, you can see the gap (with some thermal grease) between the heatsink and the CPU when I only use the plastic spacers. Using the four screws on each corners of the CPU to allow contact bends the board, as you can see on the second picture.
I suppose I could use a copper shim.
