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Power Mac G5 shuts down after 10-15 minutes

A

andersrose

macrumors newbie
Original poster
Sep 27, 2013
6
0
Hey,

My Power Mac G5 Quad Core shuts down after 10-15 minutes of use without any messages.

What could be the problem?
 
andersrose said:
Hey,

My Power Mac G5 Quad Core shuts down after 10-15 minutes of use without any messages.

What could be the problem?
Click to expand...

Could you give us some more information about your setup first?

When did this start happening?
Which OS are you running?
What display do you have connected?
How much RAM is installed? In which slots?
Do the fans kick in before it shuts down? DO the fans turn on at all?
Have you recently upgraded anything?
What accessories do you have connected?
 
Just off hand that sounds like thermal shutdown to me. Most Macs have a temperature limit that if exceeded forces an immediate shutdown in order to prevent damage to internal components.

You might try Temperature Monitor or iStat Menus to get an idea of your CPU temps. If you are exceeding 150º or so that may be the culprit. That would suggest to me (if this is the case) that a fan is not working somewhere.
 
Very hot

I've checked the temperatures now, and the CPU A (both 1 and 2) is running at around 70-85°C, and the CPU B (both 1 and 2) is only running around 25-26°C. Do you think I need to apply new thermal paste on the CPU A or something? The computer stopped shutting down now, but the fans around the CPU'S runs on absolutely full speed, which makes it sound like an airplane is taking off in my room. Also, when the Mac boots up, the fans runs normally, but as soons as it gets to the desktop, it starts taking off, and the temps says what i said before. Thanks for the help so far.

The computer is by the way totally clean of dust, there is no dust at all.

EDIT: The computer just shutted down again. I putted in under stress while checking the temps, and it shuts down when CPU A reaches 100°C..

Oh, and the specs are:
Power Mac G5 Quad Core 2.5GHZ
6GB Ram
6600 256MB

SCREEN:
Billede_2.png
 
Last edited:
Yeah, that's thermal shutdown. Something isn't right with first CPU. New paste may help but I'm no expert. Hopefully someone else might have a good suggestion.
 
andersrose said:
I dont quite understand what you want me to do..? :(

Edit: Is it possible to remove the hot CPU, and use the G5 as a Dual Core? :)
Click to expand...

Yes, it's possible to run with a single processor. But first read through those threads. Sometimes it can be as simple as too much air in the system (hear any sloshing?) or a clogged hose. I've worked on a few for other people, but I've never actually owned one of these. Several here do, so it might be best to wait for more specific advice from them.

For now, so everyone can know what we're talking about, which of these is yours:

G5Quad_pump_types.png
 
Swampus said:
Yes, it's possible to run with a single processor. But first read through those threads. Sometimes it can be as simple as too much air in the system (hear any sloshing?) or a clogged hose. I've worked on a few for other people, but I've never actually owned one of these. Several here do, so it might be best to wait for more specific advice from them.

For now, so everyone can know what we're talking about, which of these is yours:

Image
Click to expand...

The one with the black pumps :)

No, i dont hear any sloshing, and I've read through them both, and the only opportunity, for a guy like me, would probably be to remove CPU A.
 
Last edited:
andersrose said:
The one with the black pumps :)

No, i dont hear any sloshing, and I've read through them both, and the only opportunity, for a guy like me, would probably be to remove CPU A.
Click to expand...

If you have the dual pump LCS then the pump for CPU A could be bad. It could also be clogged.
 
G51989 said:
Assuming the pump isn't bad, it's not all that hard to to unclog the pump and refill the system
Click to expand...

Probably not, but I'll need to make the Mac work now. So how do I remove the CPU A? :)

Can i just remove the powercable from CPUA? :)
 
Last edited:
andersrose said:
Probably not, but I'll need to make the Mac work now. So how do I remove the CPU A? :)

Can i just remove the powercable from CPUA? :)
Click to expand...

No the motherboard will detect it and throw a stop error.

You need to completely remove the LCS, the processors will come out with it. Then remove CPU A from the LCS and reinstall the LCS.
 
alexrmc92 said:
No the motherboard will detect it and throw a stop error.

You need to completely remove the LCS, the processors will come out with it. Then remove CPU A from the LCS and reinstall the LCS.
Click to expand...

Hmmm. But wouldn't the single CPU still need to be installed in the top slot (the CPU A location)? This may not actually be a viable solution here since that's where the cooling problem is? Damn. If it were CPU B causing problems, we could just disable it with an open firmware command.
 
Swampus said:
Hmmm. But wouldn't the single CPU still need to be installed in the top slot (the CPU A location)? This may not actually be a viable solution here since that's where the cooling problem is? Damn. If it were CPU B causing problems, we could just disable it with an open firmware command.
Click to expand...


True didn't think about that. Looks like the only way to fix it is to fix the LCS (if thats the problem). I've also seen the G5 CPU's start to overheat like this when they're on their way out.
 
alexrmc92 said:
True didn't think about that. Looks like the only way to fix it is to fix the LCS (if thats the problem). I've also seen the G5 CPU's start to overheat like this when they're on their way out.
Click to expand...

Aye. Haven't there also been some cases where the temperature diode malfunctions and reports temperatures higher than what are actually occurring? And if it is the CPU itself, and not the cooling system, then the plan could work. CPU A could be removed and then B swapped to the A position.

In most cases these symptoms point to an LCS problem, but that's not 100%. And I don't really have a good sense of what those percentages actually are.

I've PM'd OrangeSVTguy in hopes that he will have time to take a look at this thread and offer some additional troubleshooting steps and viable options. He has done complete overhauls of these cooling systems and has also run them with a single CPU.
 
Swampus said:
Aye. Haven't there also been some cases where the temperature diode malfunctions and reports temperatures higher than what are actually occurring? And if it is the CPU itself, and not the cooling system, then the plan could work. CPU A could be removed and then B swapped to the A position.

In most cases these symptoms point to an LCS problem, but that's not 100%. And I don't really have a good sense of what those percentages actually are.

I've PM'd OrangeSVTguy in hopes that he will have time to take a look at this thread and offer some additional troubleshooting steps and viable options. He has done complete overhauls of these cooling systems and has also run them with a single CPU.
Click to expand...

Thanks for PMing me. Looks like it could be the pump or CPU that is failing but most likely CPU. It's easy to swap the CPUs. The whole LCS assembly comes out in one piece and the CPU cards are held in the bottom of the assembly with 10-12 little hex sided screws. You will need a long "+" and Alan key to remove all the screws holding the LCS assembly in.

Also would be good to check if both pumps are working. And apply new thermal paste to see if that drops any temps. If you change out the fluid, I recommend using Feser 1 fluid. I've modded a few LCS assemblies with new tubing and the fluid mentioned above. Be sure to check for leaks too.

If you check the model #s, on the CPUs, 2 different ones I believe there were, I have a few sets of them but I have t used them in years so it would be crap chute if they still work or not. I also have a few extra LCS assemblies in both dual and single pump versions, both worked and no leaks.
 
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