Power Mac G5 overheating - LCS problem (photo)

Hi to one and all,

I purchased a Power Mac G5 Quad Core (late 2005) last month for my small business, as I was in need of some firepower to out-muscle my old computer. I do music production and things were starting to slow down when adding in plug-ins. Unfortunately I was ignorant, and trusted a failing auction company, spending £350 on this very large paperweight which showed up to my door full of dust and unable to startup.

To cut a long story short, I used canned air and curiosity to clean the whole thing out, and managed to get it started up for the first time.

However, it often shut back down on startup and when I checked the stats, CPU B Diodes 1 & 2 were running around 89/91* whilst CPU A Diodes were running around 33*, which are where I believe they should be.
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THE QUESTION!

Why does one CPU pair run so hot whilst the other runs so low? It seems as if either the workload is being routed solely to the CPU B pair, or that the Liquid Cooling System (LCS as we know it), is only cooling CPU A very well and not cooling CPU B very well at all.
This sounds like a thermal conduction problem, leading to either a malfunctioning LCS or even poorly applied/dissolved thermal paste. (I've heard the thermal paste used was highly toxic so any honest answers regarding changing this, please consider safety )

There is hard green stuff around the tube connections of the LCS and no sign of any leakage, this seems like glue but if anyone has any other proven suggestions? How do I check the LCS is pumping and working well? Or that it is full with liquid?




Thank you in advance for any time taken to read or help, I've trawled every forum out there and can't find a specific answer to this problem.

Cheers,
Tryp

The liquid cooled G5 did have huge problems with leaking coolant, that green stuff you mention. This comes about when O rings etc fail with time and corrosion. You might google for a service manual. Not highly recommended the liquid cooled G5's alas. Sounds as if coolant has got into the CPU that is running hot. This may be of some help:-

http://www.xlr8yourmac.com/systems/G5_CoolantLeak_Repair/G5_CoolantLeak_Repair.html

Hi Harryb2448,

From the pictures are you certain that the green stuff is coolant? To be crystal clear that stuff is solid and feels like solid plastic when I tap it, which made me think it was a previous repair and they glued the ends of the tubing to make sure no coolant leaked again.

I haven't seen any corrosion on the pad below or between any components as seen in the first photos of that xlr8yourmac.com post, as I didn't remove the copper pads which were bolted to the CPU cards, which was mainly due to hearing that the thermal paste was toxic. Can you confirm that it is (reasonably) safe to get in about with a pair of gloves maybe, and I'll get straight to it.

I'll give anything a try, as I said before I've wasted £350 already and want to have a good crack at repairing this thing to sell on as fully working.

Thanks

Think the CPU temperature differences may well indicate a leak It would take a daring man to tackle with one of the beasts. Look for threads by member baggss who had the same model and his adventures with it.

Thanks Harry, I'll give baggss a search and see how he got on, I'm ideally looking to revamp only the broken LCS loop to CPU B and leave the working CPU A loop well alone. Oh what fun we had, on a one horse open-sleigh.

Hate to suggest this but a far better option is an Intel powered Mac such as a 2008 Mac Pro.

You bought a computer from 2005 (and paid waaaaay too much for it) and are surprised that it is having problems? Really?

And this eight-year-old computer replaces your "old" computer? Oh dear ...

I *don't* hate to say it: this was a really bad idea. Buy something made this decade.

chas_m said:

You bought a computer from 2005 (and paid waaaaay too much for it) and are surprised that it is having problems? Really?

And this eight-year-old computer replaces your "old" computer? Oh dear ...

I *don't* hate to say it: this was a really bad idea. Buy something made this decade.

Click to expand...

Thanks for the input Chris, very helpful. I actually had thousands of pounds kicking around my bank account unused, but this one caught my eye and seemed like my dream computer. From then I knew, I just had to have it. /sarcasm.