Restoring an old G5 Quad

[Leite28]

Hi there!

Last summer I bought an used top of the line Power Mac G5 Quad, with 2 G5 Dual 2.5Ghz CPUs, 7GB of RAM, 2 SATA HDDs and the powerful FX4500 graphics card. It even has an AirPort Extreme installed!

While it's a powerful machine - for music and photo editing - the Mac is overheating a lot. And by a lot I mean that the computer freezes and turns on the red overheat light right after entering desktop.

I've tried to run with just one CPU enabled on the Open Firmware, tried to reinstall OS X, tried to enter safe mode, cleaned the whole computer, nothing.

I've successfully toke apart the LCS with the CPUs of and cleaned all the dust of the radiator grills. I've also read that many people have rebuilt their LCS and from what I know I have3 the worst of them all: the dual Delphi pump Cooligy LCS.

I feel bad for having this amazing computer just stop in my garage while I use my 2009 iMac - with the low-end 9400M - to edit all my photos in Aperture, so I wanted to make this beast purr again.What can I can do to make it stop overheating and bring it back to life?

Best regards,
Leite.

 

[Frost7]

There's a lot of misinformation and FUD out there about Quad LCSes.

For one: There are not 3 types, there are only 2. The mythological "Panasonic LCS that was perfect but went in very few Quad G5s" doesn't exist and never did.

For two: The single-pump is actually the older model, but Apple used both simultaneously. There's no data to suggest either is more leak-prone or failure-prone than the other. I've seen both go down. The big worry about leaks and failures stems mostly from earlier LCS-equipped G5s, like the Dual 2.7s, being mentally associated with Quads.

Not to say they don't fail; they do. But either LCS can fail over time when you're talking 8 years of service.

As far as what you can do... I wouldn't suggest opening and flushing the LCS unless you really, really know what you're doing in that area. A better solution would be to thoroughly clean any and all dust and junk out of the system (as you've already done), then replace the thermal paste on the processors with fresh. DO NOT use AS5. I recommend AC MX-4 for G5s.

This probably won't solve your problem, as an overtemp is usually due to either the LCS being plugged up and not cooling properly, or the processor having suffered a failure that's causing it to generate far more heat than it should. But it's worth a try.

Most likely you'll need to hunt for a replacement CPU/LCS module on eBay or wherever else you might be able to find one.

A workaround is to see if you can get Temperature Monitor installed and running in the short time before you experience overtemp: http://www.bresink.com/osx/TemperatureMonitor.html

If you can get that installed and get temperature readings before shutdown, you can determine if it's only one of your CPUs overheating. If so you could pull the faulty CPU and just run with one CPU until you locate a replacement. That would at least get it in usable condition.

I ran into this on one faulty G5 a couple of years ago. CPU B was generating insane temperatures, but the LCS and CPU A turned out to be fine. Replaced CPU B, problem solved.

 

[Leite28]

(…)

As far as what you can do... I wouldn't suggest opening and flushing the LCS unless you really, really know what you're doing in that area. A better solution would be to thoroughly clean any and all dust and junk out of the system (as you've already done), then replace the thermal paste on the processors with fresh. DO NOT use AS5. I recommend AC MX-4 for G5s.

(…)

Most likely you'll need to hunt for a replacement CPU/LCS module on eBay or wherever else you might be able to find one.

If you can get that installed and get temperature readings before shutdown, you can determine if it's only one of your CPUs overheating. If so you could pull the faulty CPU and just run with one CPU until you locate a replacement. That would at least get it in usable condition.

I ran into this on one faulty G5 a couple of years ago. CPU B was generating insane temperatures, but the LCS and CPU A turned out to be fine. Replaced CPU B, problem solved.

I was thinking of flushing the LCS… And here's why: when I bough the computer, I tried it on the sellers home and it worked. I checked System Profiler and I asked to open the computer to check for spillage, all seemed OK. However, when I arrived home the computer started overheating. My guess is that some residue deposit became loose during the transportation, not allowing the correct flow inside the LCS. But I bought a stick of MX-4 some time ago and it's still OK, so I'll try that tomorrow.

The problem with the replacements is the price. I made a great deal where I paid 200€ for the machine because here in Portugal Macs are not that common and are heavily overpriced. I once saw a post on OLX for a used iBook G4 for the price of a used 1st gen MacBook, about 300~350€!

Ebay has lots of replacements but the shipping costs are absurd. They cost half of the price of the part. That's my main problem. Once I found a store in Germany that had refurbished LCS units but I can't recall the store's name.

The Mac has iStats installed, but it normally overheats before I can check it. I once tried to disabled one of the CPUs in the Open Firmware with no results.

 

[Cox Orange]

(...) DO NOT use AS5. I recommend AC MX-4 for G5s.

(...)

Why? Could you elaborate?

Is it the texture? After reading some about thermal compounds and pads, I got the impression that cooling wise the differences are in the range of measurement faults and so one can only decide by the characteristics of the kinds (how greasy it is, whether it reacts with copper, being conductive or not, etc.)

I found this http://skinneelabs.com/2011-thermal-paste-review-comparison/2/ but I do not know, if the figures tell anything... (like I said above).

My question might be needless, anyway, but did you test any of the following and can tell something about them:
Prolimatech PK1 and PK-3
Zalman ZM STG1
Gelid Solutions GC-Extreme / Phobya HeGrease Extreme (rumored to be the same)
Thermalright Chill Factor 3
Noctua NT-H1
OCZ Freeze
Nanoxia Heat Buster NX-HT-1000

I would have inlcuded the Arctic Cooling MX-4, too, if you had not just mentioned it. I have bookmarked this list somewhen, but I do not remember what the criteria was, why it put them together on the list...

You say "for G5s", so for G4s AS5 is still the best (or maybe just the best known)?

Most likely you'll need to hunt for a replacement CPU/LCS module on eBay or wherever else you might be able to find one.

I heard of people replacing CPUs in G5s and having problems with it afterwards andd they said it required using the ASD DVD...?

 

[Frost7]

The reason is it's electrically conductive, requires a curing process that is a huge waste of time, and has no real benefit over newer, better compounds that have neither of those downsides.

The urban legend and obsession with AS5 on the internet is just a pet peeve of mine. It was great like ten years ago. I used to use it too. Now, not so much, and I never use it.

The curing time is why I highly recommend not bothering with AS5 on G5s that already having overheating issues. You'll just exacerbate the problem and it'll never cure. Meanwhile MX-4 works just as well if not better, and works the moment it's applied. Seen the same problem with people doing that to their original PS3s trying to prevent the YLOD and they end up causing it.

It may fly in the face of web forum wisdom, but there is no good reason to use AS5 over a modern thermal paste. I like MX-4 because it does as well as MX-2 used to, and has worked very well for me when servicing finicky G5s and iMac G4s.

I heard of people replacing CPUs in G5s and having problems with it afterwards andd they said it required using the ASD DVD...?

Yeah, if you do anything other than put the same CPUs back in the same place, you'll need to get ahold of ASD somehow so you can calibrate the cooling system. If your existing setup is failing, though, it's that or scrap your G5.

 

[Intell]

The reason is it's electrically conductive, requires a curing process that is a huge waste of time, and has no real benefit over newer, better compounds that have neither of those downsides.

AS5 isn't electrically conductive.

Not Electrically Conductive:
Arctic Silver 5 was formulated to conduct heat, not electricity.

Source: http://www.arcticsilver.com/as5.htm

Besides the curing time, there's no problem in using it in any machine.

 

[Frost7]

You're right, capacitive, sorry, not conductive.

 

[Sepultura]

Lucky you can even boot.

Is LED #7 on?

I plan to rip mine apart again to see if one CPU is dead.

 

[Intell]

You're right, capacitive, sorry, not conductive.

It still won't damage the CPU or machine under normal circumstances.

 

[Andropov]

It still won't damage the CPU or machine under normal circumstances.

It wouldn't damage the CPU or machine even under abnormal circumstances. Unless you apply it improperly, of course (i.e, dropping it over the motherboard). But every thermal compound can be dangerous if used improperly, so...

AS5 was a great thermal compound a few years ago. Today, it's a good, cheap thermal compound. The difference with other compounds is still pretty small, I doubt you'll burn it by using a thermal compound that performs 3ºC hotter than the best one out there.

 

[Frost7]

AS5 was a great thermal compound a few years ago. Today, it's a good, cheap thermal compound. The difference with other compounds is still pretty small, I doubt you'll burn it by using a thermal compound that performs 3ºC hotter than the best one out there.

For normal usage, sure, but if you're bumping up against overtemp already as this thread concerns, that little bit can make all the difference at the very least for isolating the issue and delaying shutdown a little while longer. Especially since it needs curing to boot and that's not going to happen.

Far as improper application... you should see what some people do with thermal paste in their machines. The more idiot-proof the better. :/

 

[alexrmc92]

I'm doing the same project as you. The dual core G5 chips run very hot and once they overheat once they are almost never the same.

The late 2005 LCS is made by delphi, but is much better than the previous generation LCS. It rarely leaks or has coolant deterioration. The easiest way to drain it is to remove the lower half of the cpu blocks. One drained use loctite on the screws when putting it back together.To fill it cut one of the inlet lines and insert a tee fitting. use another hose attached to the tee to fill the LCS and cap it once it's full. Premix automotive coolant works well, you can also use coolant made for computers but make sure it has anti corrosion additives.