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PostPosted: Tue May 22, 2018 12:19 am 
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Location: Ukraine
I have bought Power mac quad with dead LCS. So I refilled it with new coolant and it worked fine until I noticed leakage (clamps I used were not the right diameter) and I rebuild whole unit once more. But now when I try to Thermal Calibrate it shows error "Processor max. temperature exceeded" on both CPUs. And it boots to Leopard fine showing idle core temps around 45-50 C. Thermal paste is reapplied as I did previously.
Any thoughts s on that?


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PostPosted: Tue May 22, 2018 8:01 am 
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It kind of sounds like the system may have decided it needs recalibration, which is usually not something you want to have to do. Do you know if the CPUs went back in the original sockets with the same heatsinks attached? This is rumored to help keep the system from deciding that it needs recalibration.

Unfortunately I'm not an expert on these systems. I've worked on a lot of G5s, mostly iMacs, but got out of that business before I had to touch the LCS towers. Maybe BDAqua or monkeyboy will have other thoughts. A newer member Fire Angel also has a lot of experience working on the quad G5.

- Anonymous


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PostPosted: Tue May 22, 2018 12:56 pm 
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The most experience I have with LCS G5s is walking in after the LCS has failed, all the fans are running 100%, and the system is dead. Those experiences are why I went out of my way to get an air cooled G5.

Did you use something like Artic Clean to clear off the residue of the previous thermal compound? Some of that stuff, especially older caked on compound, is hard to remove without a specialty solvent (some solvents will leave a residue behind that interferes with the effectiveness of the new compound).


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PostPosted: Tue May 22, 2018 1:12 pm 
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Welcome aboard Andrew ! :welcome:

Sadly I don't know of a cure for this, but I suspect if it's not a physical problem with the CPUs, that Open Firmware would hold the unknown answer.


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PostPosted: Wed May 30, 2018 2:38 am 
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Yes, I cleaned off old paste with pure alcohol. Yesterday I started all over - flushed coolant, changed tubes, reassembled whole damn thing again))) What I noticed is that because of longer tube used on z-tube, water block is not parallel to CPU board. Maybe that is what causing the problem. Gonna try installing unit and check temps again


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PostPosted: Wed May 30, 2018 3:06 am 
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I hear that purging all the air can be a problem.


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PostPosted: Wed May 30, 2018 2:41 pm 
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Yeah, the amount of purge valves in a modern car cooling system is quite amazing. Literally every spot where air would tend to collect they have a valve sitting there to purge it. They actually design spots for air to collect so it doesn't collect inside the block or head or someplace where you can't easily get rid of it. I've read that G5 LCS doesn't have quite that same level of sophistication. I've heard of guys actually rotating their systems while turned on to encourage air to extricate itself to a spot where it can be purged.


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PostPosted: Sun Jun 03, 2018 11:08 pm 
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It was air! Air in water blocks. It is best to use distilled water (I tried using G11 coolant, but it is not safe for health) and pump it trough system under some pressure. Now I have 29-31 C on all cores in reduced CPU mode on idle. And system is almost quiet as iMac G4


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PostPosted: Mon Jun 04, 2018 12:01 am 
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Congratulations!

Thanks for letting us know what you did to solve it. How did you pump it through the system? Could distilled water, since it doesn't have any anti-corrosion agents, lead to future problems?

- Anonymous


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PostPosted: Mon Jun 04, 2018 12:27 am 
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Using this)))


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PostPosted: Mon Jun 04, 2018 12:32 am 
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I think water sure can lead to more problems in future - but its gonna be a far future))) I dont think aluminum is very sensitive to corrosion. Distilled water is easy to work with - not a problem if you spill it all over the place. But best is to use G13 coolant, propylene glycol is harmless


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PostPosted: Mon Jun 04, 2018 5:17 am 
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Great news. Air and liquid cooling systems don't mix. Last time I changed a car radiator it was overheating like crazy until I got the air out.

I would certainly try putting some antifreeze in the mix, it's not just for freezing, it raises the boiling point of the mixture, which is important because steam (water that's transitioned from liquid to gas) creates the same issues as air. You don't have to put a lot into the mix, a little goes a long way.


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PostPosted: Mon Jun 04, 2018 12:40 pm 
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Great news Andrew, thanks for the report! :)


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