G5 Quad - ASD 2.6.3 Freezes and Overheat Light On

[dbdjre0143]

As many of the regulars here know, I just acquired a new-to-me G5 Quad. Today, my power cord I've been waiting for came in. I burned a copy of ASD 2.6.3, which I then booted on my Powerbook to make sure it worked, which it did.

I popped it in the G5 and tada, it started to boot. However, when it got to the blue "Apple Service Diagnostic Loading" screen, it froze. This happens consistently.

Digging deeper, I noticed that a red light is on near the front of the case, labeled "Overtemp". The problem is, the machine has barely started to boot. When that light comes on, the CPU heatsinks are still cool to the touch. Sometimes after awhile the machine shuts off, I assume due to the supposed overheating. However, even when this has happened, the CPU heatsinks were barely warm, not uncomfortable to touch.

It does seem like the LCS pumps are running. I have what I assume is a "two-pump" Delphi system, since it has two separate black housings which I assume are pumps on top of the CPU heatsinks. There is also a sticker labeled "Cooligy" at the base of the LCS enclosure. While the fans sounding like a jet drown out any noise the pumps might make, I do feel a slight vibration laying my hand on them while the machine is on. I started it once with their power cable unplugged and could not feel the same vibration, so I feel confident they are at least trying to work.

So, I know from my highly unscientific "touch"-test that the CPUs (or at least the heatsinks) aren't getting too hot, but I can't get the machine to boot to the ASD DVD to calibrate the cooling system so it knows that. I'm hoping some of the super knowledgable folks around here have fought this battle and can share some wisdom with this G5 newbie.

Thanks as always for being awesome!

 

[AphoticD]

It sounds like the thermal paste is kaput. I would take the LCS off the CPUs and apply fresh paste. You don't need to drain the coolant or anything risky, just carefully remove the LCS, then re-apply the paste between the CPUs and the coldplate on the underside of the cooler mounts.

See here: http://www.xlr8yourmac.com/systems/G5_CoolantLeak_Repair/G5_CoolantLeak_Repair_p2.html

Don't cheap out on your paste for the G5s. I've had to re-paste my air-cooled G5s due to using a cheap product in the past. I'm using Thermal Grizzly Kryonaut with great results on my Dual Core 2.3GHz and my DP 2.0GHz now. I have just ordered some more (out of the UK) to do my Quad next.

( Yeah, I picked up my first Quad last weekend! )

 

[Dronecatcher]

Is the clear plastic inner shield there - judging by you putting your hands on components, it sounds not? A G5 doesn't like that shield not being in place (there's a sensor to detect it's presence.)

 

[dbdjre0143]

Is the clear plastic inner shield there - judging by you putting your hands on components, it sounds not? A G5 doesn't like that shield not being in place (there's a sensor to detect it's presence.)

Yes it is there. I removed it for my touch-testing. Its presence is also correctly tested, because the LEDs light up like a Christmas tree when I remove it with the machine on.
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It sounds like the thermal paste is kaput. I would take the LCS off the CPUs and apply fresh paste. You don't need to drain the coolant or anything risky, just carefully remove the LCS, then re-apply the paste between the CPUs and the coldplate on the underside of the cooler mounts.

See here: http://www.xlr8yourmac.com/systems/G5_CoolantLeak_Repair/G5_CoolantLeak_Repair_p2.html

Don't cheap out on your paste for the G5s. I've had to re-paste my air-cooled G5s due to using a cheap product in the past. I'm using Thermal Grizzly Kryonaut with great results on my Dual Core 2.3GHz and my DP 2.0GHz now. I have just ordered some more (out of the UK) to do my Quad next.

( Yeah, I picked up my first Quad last weekend! )

Congrats on your first Quad! Hope yours has a bit better luck to start than mine. I'm ordering some Kryonaut now. I had thought that perhaps it could be a thermal paste issue since the coolers stayed relatively cool, but it still seems odd that it heats up so quickly without them getting more than slightly warm. I've had worn out thermal paste on other machines and none behaved quite that badly, but none were G5's either.

 

[SuperKerem]

I’ve tried replacing the thermal paste and at one point even removed one of the processors and ran my “Quad” air cooled with 2 x 2.5GHz cores. My best guess currently is that the coolant needs to be replaced in the LCS, but this requires quite a lot of dedication to do.

https://68kmla.org/forums/index.php?/topic/26539-how-to-repair-a-g5-quad-dual-pump-lcs/

 

[Amethyst1]

( Yeah, I picked up my first Quad last weekend! )

Are you going to build your own Big Mac?

 

[dbdjre0143]

Well, I tried the repaste over the weekend, and sadly it didn't help. Looks like I'll have to go down the rabbit hole of rebuilding the LCS. Not necessarily looking forward to that job...

 

[pl1984]

Well, I tried the repaste over the weekend, and sadly it didn't help. Looks like I'll have to go down the rabbit hole of rebuilding the LCS. Not necessarily looking forward to that job...

I hear ya. My recommendation is to take your time, don't rush it. Approach it with a hobbyist state of mind and enjoy the learning experience. Then, when others have to rebuild theirs, you can share your knowledge with them.

 

[mduser63]

I’m in the exact same boat except that mine has the single pump Delphi LCS. I got all the parts and supplies to rebuild the LCS today. Planning to make a project of it this weekend.

 

[AphoticD]

I’m in the exact same boat except that mine has the single pump Delphi LCS. I got all the parts and supplies to rebuild the LCS today. Planning to make a project of it this weekend.

Good luck! It would be great to see some photos or videos of the project.

Mine is also the Delphi single pump LCS. It appears to be running okay, but a previous owner had overhauled it at some stage and botched one of the clamps. It isn't leaking but does look questionable. I think I'll rebuild the LCS once all of the other missing parts come in (Front fans, PCI divider plate and a few others). I have a fresh tube of Thermal Grizzly Kryonaut ready to paste onto the CPUs.