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Excellent write-up on LCS Servicing, Quad G5

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#1 beachycove

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Posted 28 May 2013 - 04:17 PM

There are a handful of us who like the G5, and want to keep the machines running. The rest of you can ignore this post!

The following link could be of use to someone trying to quieten a Quad G5, and to prolong its life: http://www.saunalaht... ... epair.html . Notice the graphs at the foot of the page, as 10ºC lower CPU temperatures at idle and 40ºC lower under load would make all the difference in dealing with fan noise. There are some further links re. cooling systems in the G5 at the bottom.

I have serviced three air cooled units (essentially just thermal grease renewal and cleaning out dust, followed by recalibration) with excellent results, and these are very easily done (contrary to what some people think), but the liquid cooled systems especially make people shudder. The writeup takes much of the complexity out of the whole question.

I believe that there were two LCS systems in the Quad G5, so be aware of that — your LCS may differ. All the same, the author has documented not only the basic plumbing and mechanicals, but crucially, the presence of sediments in the radiator fluid used after several years, leading to clogged filters. There will be a related need to clean out the radiator and clean or renew the hoses.

As in your car's cooling system, the lifespan of radiator fluids is limited, and when sedimentation occurs, the works are bound to get gummed up. The key thing in the LCS is to keep it running optimally, as the temperature thresholds are really rather slender, so this is good to know about.

My "new" Quad G5 is still working well, but it could still afford to run at slightly lower temps, so methinks I'm going to service it sometime over the coming months.

#2 uniserver

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Posted 28 May 2013 - 07:50 PM

There is only a handful of people that like the G5?

I didn't think they were that terrible.

I would assume with a Lights dimming Quad core G5,
You should still be able to do some slightly useful things with them.

#3 TheMacGuy

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Posted 28 May 2013 - 09:17 PM

I would assume with a Lights dimming Quad core G5

Did they really suck down that much energy?

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#4 uniserver

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Posted 28 May 2013 - 09:40 PM

well the tower alone sucks up 500 - 600 watts

Doing about anything online is stressful to a G5, They have to work so darn hard at doing anything useful.
where an intel machine does the same thing at 25% or less utilization.

#5 Anonymous Freak

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Posted 28 May 2013 - 10:16 PM

The late 2005 model carried a 750W power supply, which is a lot, but there are PC power supplies (and many server power supplies) that are much larger.

My dual-proc server at home has a dual-800W power supply. (It's meant to be for redundancy, so it should only draw 800W max.)

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#6 Cory5412


    Daring Pioneer of the Future

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Posted 29 May 2013 - 03:12 PM

I've stickied this as it's a good resource.

#7 Cory5412


    Daring Pioneer of the Future

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Posted 14 March 2014 - 01:28 AM

I'm sure some parts might be different, but I came across this wonderful guide on how to disassemble the LCS. This is for the DP 2.7GHz Early 2005 (my model actually), but it might be useful on your Quad disassembly.


#8 XBHS1997

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Posted 15 September 2014 - 09:05 PM

Thanks for the link, I have 3 trash-found Power Mac G5 to repair (I believe one is a watercooled 4x2.5)!

Newton H1000, SE/30, Portable, 2x PB 145, PM 8500/180, PM 4400/200, Perf 5200, PM G3 300 Beige, 2x PM G3 233 DT, PB G3 WS 233 (350 now), iBook G3 DV SE 466 Graphite, 2x iMac G3 TL 333, 15x iMac G3 SL (350 – 600), PM G3 B&W 300, PM G4 AGP 350, PM G4 QS 800, iMac G4 800 and 1.25 (17"), 3x PB G4 (15" 1.5 Ghz, 17" 1.33 Ghz, 17" 867 Mhz), 6x PM G5 (1.8/1.8 DP/2.0 DP/2.5 DP/Quad), 2x Mac Pro 2x3.0, Mac mini 2.0, MacBook 2.0 Black (MB 1,1), Xserve G5 1x2.0, 2x Cinema Display, 2 CRTs, other stuff; and my iMac Late 2009 27". Mostly trash-picked or saved.

#9 Schmoburger

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Posted 09 February 2015 - 05:34 PM

I now have 2 of them after my 2.0 DP all but died... replaced with a late-2005 2.0 Dual Core. Love both of them :D


Going to possibly see about reflowing the board on the dual processor and see what I can make happen, as it seems a waste of a great computer having it as a door stop.

iMac, PB G3 & B+W boffin... with 40 or so Compacts, Performas, LC's, OW Powermacs etc to keep it fun.

My new blog of all things remotely Mac and sometimes not... http://macaddictisnotdead.blogspot.com.au/

#10 LarBob

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Posted 25 June 2016 - 09:38 PM

Since the service guide link is apparently not working right now, here's an archived link.


#11 daveosx

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Posted 27 June 2016 - 07:39 AM

Mondo frustration

I recently started having screaming fans on my G5 Quad PCIe

So I went ahead and disassembled and complete cleaned the whole thing.

I was having issues with the ASC pump test causing an instant overheat condition

So last night I went ahead and serviced the LCS cleaned everything out nicely no leeks 

However I still have the instant overheat on calibration or pump test

So now I am looking for a pair of processor cards


Do any of you know where I can get new ones ?

Any one have the part numbers I am willing to get new from apple ?


Also I have heard of a way to put a non liquid cooling system on these back when everyone was dripping.

Does anyone remember that mod and have info? Found it!



I see an issue in the guide you will need to provide another 4 pin fan to plug into the pump harness or it will fail.

I was thinking that you could use the fan to cool the ram or video cards.

I am going to eBay a dual 2.0 passive cooler and try before I buy a set of processors.


The Mac still boots and runs fine never had it stall or overheat while using it.

Even when using handbrake just the fans come on full speed all the time this is deafening as I have the G5 and a Mac pro next to each other in a cabinet above the monitors so it is above eye level and the G5 screams.

The G5 sounds like a dell server like it has Delta High pressure fans.


Also I will be updating a PM MDD wind tunnel with some corsair fans and will post results and part numbers.

Edited by daveosx, 27 June 2016 - 07:59 AM.

Back to Mac for joy

#12 daveosx

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Posted 07 July 2016 - 09:41 PM

Turns out both my main pump and my spare lost head pressure so no flow through the coolers.

I milled some brackets last night out of nylon and mounted two NIC L32 thermaltake cooler to teh procs.

Tonight I plan to sort out the air flow and the small 4 pin fan to fool the MB into thinking there is a pump present.

My intent to use the 140mm fans with the heat sinks was thwarted by lack of space.

Now I am thinking of some aluminum duct work to direct the airflow up the center and out the sides to the back.

The smaller fan will blow air under the heatsinks to the back.


At this point with no budget to replace the pump or LCS I figure I would cotch up a solution and see if it works.

If it does great if not I am in the same boat anyway.


No pump no thump

After 12 years `and one replacement under warrenty this mac owes me nothing.

Back to Mac for joy

#13 360alaska

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Posted 08 July 2016 - 01:50 AM

Do you have a single or dual LCS Quad? I may have a spare pump...

Edited by 360alaska, 08 July 2016 - 01:51 AM.

#14 FacnyFreddy

  • 6502

Posted 05 January 2017 - 03:00 PM

One of my close friends had a dual cpu G5 and it was a bit noisey from the start. His had 8GB of RAM and he did full time video editing with it.


One way to keep the fans from running all the time was to put in a "puller" fan behind it that helped move air out. I think he had a 120 or 140mm fan with a cowling around the back of the case and then shot the air upwards. I only saw it once....

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