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Mac Pro 4,1 Northbridge plastic to screw - need answer quick

45 minutes of Geekbench 2 stress test

CPU A Tdiode 168
CPU A HeatSink 139

CPU B Tdiode 150
CPU B HeatSink 118

IOH HeatSink 131
IOH Tdopde 198

System Ambient 79

Booster 1 1370 rpm
Booster 2 1370 rpm
Exhaust 735 rpm
Expansion Slots 796 rpm
Intake 734 rpm
Power Supply 600 rpm
 
My 2 plastic retainers has been brooken so, yesterday i fixed with two bolts and replace the grease on booth processors and t-diode sensor, the temperature has descended drastically from 129°C to 80°C on the t-diode, before this the machine keeps hanging on all the time and must to keep the fans at medium speed all the time, no hangups since the fix. Even so, my other MacPro has 65°C on t-diode mostly of the time, maybe need to put more grease on it.
 
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More on this macPro heat think issue

Add my name to the list of those who have had the heat sink pop off the IOH Tdiode (Northbridge). I realize this is an old thread but it was so incredibly helpful to me that I feel the need to weigh in for any future readers who might encounter the same issue.

In my case my mac just suddenly wouldn't boot one day. No chime and the fan in the graphics cards running at full tilt. The red LED on the processor board was clearly visible when I opened the machine. Thanks to this thread and a few others like it I was able to find the problem in under half an hour. I could hardly believe it when the little black screw/clip rolled out from the processor board as others had posted.

The black plastic screw/clips that hold the memory chip's heatsink in place are absolute crap. I in fact broke the second one when I was trying to remove it. Fortunately in my case I found the spring for the first broken one when I opened my case the first time. It just rolled out from under the processor board.

Apple wanted to charge me for a whole new logic board despite my literally bringing them the broken part and showing them the problem. That would have cost several hundred. Even the usually robust semi local mac repair shop that I've relied on before was unwilling to attempt this repair. But for 50 cents at the hardware store and $8 for some arctic silver my machine is back up and temps look great.

My suggestion for anyone who encounters this is to purchase two small nylon screws and nuts that are as close in size to the black plastic clip-screws as possible. In my case I couldn't get ones thin enough to fit through the board so I had to drill out the holes a little bigger (nerve-racking, that was). I tried to match what I thought to be the spring tension with the new screws but it was tough to say whether or not I got it really close. Regardless, my system is idling with the north bridge at 41oC now.

Granted the fix was a risk since I feared that the chip had been fried in the process of running the machine without the sink. Obviously the temp sensor saved things as it should. With the sink off the chip I assume that on boot the temp sensor function for the chip itself detects too sharp a rise in temp and cancels boot. It's probably sensing the high rate of change in the temp, not the actual temp. I had thought that there was some kind of electrical continuity between the ends of the sink but that proved to not be the case on closer inspection.

At any rate, this is really a lame issue and one that i feel that Apple should be addressing. Despite two trips to two different apple stores and three or four phone calls to tech - just to try to get some satisfaction - I got nowhere. So this is truly a case where it's going to be you, yourself, doing the repair. This is not something that should be happening to these machines.
 
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Can you provide more info on the hardware you used?
Did you use a spring now or is it a nylon nut and a bolt?

I have noticed now that the temp is 110C now and I've decided not to use the computer anymore.
Apple store wants to replace the CPU tray.
 
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adam9c1 said:
Can you provide more info on the hardware you used?
Did you use a spring now or is it a nylon nut and a bolt?

I have noticed now that the temp is 110C now and I've decided not to use the computer anymore.
Apple store wants to replace the CPU tray.
Click to expand...

I can add a few details, as I also noted loud fans and very high northbridge temps (high 90's C, with the heatsink temp about 30 deg C below that). When I looked it seemed like at least the nylon rivet that is visible between the two processor cooling towers was gone. I looked around at a local computer shop and found a small fan kit that appeared to use nearly the same (same length, and width) pins. I bought it and pushed on pin down between the towers without any disassembly into the hole left by the missing pin (which I was able to recover... its not still rattling around in there!). When I did this though the northbridge heatsink was jostled a bit, and I think the second clip gave way. When I booted up I could not keep the machine running for more than a few minutes under load, and the northbridge temp was hitting the report ceiling of 129.6 C and followed shortly with a machine freeze/crash.

I still had three good pins, so I resolved to do a tear down. To fix this you need to pull off the CPU heatsinks (and clean the gunk from the CPUs and sink, pull off the CPUs, unscrew the board from the housing plate, remove the old clips holding the northbridge heatsink on (if one is still on replace it while you are there... they will break later anyways). The 129 degree heat was tough on the old northbridge grease. I worked it over pretty good with Arctic Fox cleaner and isopropyl alcohol. but I could not remove the old layer... it looked more like thermal adhesive tape or something. Anyway, I scrubbed it as best I could then just added new silver grease to it, and the two CPUs. Reassembled with new plastic/nylon rivets from the small fan I bought, and put everything back together.

Currently running NB temp is steady at 60.1 C and the heatsink 12-13 deg C lower than that. Nominal! I threw the fan away, but I'll stop at the store tomorrow and get a make/model, and post here for anyone that needs compatible rivets for the repair.
cool.png
 
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I used pins from a new CPU heat sink too. Has been rock solid for months.
I use tgpro to check temperature.
 
iStatMenus I like best, look for the I/O Tdiode.
When the rivets are still intact, try to wiggle the NB module, you should be able to 'feel' whether the cooling paste is dry or not.
Sofar all the MB rivets I replaced had dried out paste.

Take of the plastic ring and add the old spring, it will give better tension to the NB module.
 
Someone else here suggested the use of zip ties to lock down the heatsink before. He said it worked well for him.

Edit:
Here was the original suggestion
 
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If you haven't tried, why do you knock it? Seems pretty close minded...

Here was the original suggestion.
[doublepost=1488315552][/doublepost]What's the matter? No more snarky replies?
 
joebclash said:
Do you put the old spring over the cover? I'm using my mac pro for pro tools only. Recently I'm getting alot of crashes and shut downs. I'm starting to think it's the northbridge. How do you measure the northbride temps? What software are you using?
Click to expand...

I'm a big fan of TGPro (it's not expensive at all and support is stellar).
 
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pastrychef said:
Someone else here suggested the use of zip ties to lock down the heatsink before. He said it worked well for him.

Edit:
Here was the original suggestion
Click to expand...

I went with arctic alumina thermal epoxy adhesive when mine broke - http://www.arcticsilver.com/arctic_alumina_thermal_adhesive.htm

Northbridge temps are MUCH better than they were with even the stock, unbroken clips and the factory thermal grease. Just keep pressure on it for a few hours after mixing, and good to go. :)
 
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pastrychef said:
If you haven't tried, why do you knock it? Seems pretty close minded...

Here was the original suggestion.
[doublepost=1488315552][/doublepost]What's the matter? No more snarky replies?
Click to expand...

I would recommend that everyone avoid solutions that do not provide for thermal expansion. Don't use a nut and bolt, or zip ties. As the bridge/sink expands with heat, these solutions will alter the pressure applied to the bridge. That is why the stock rivets were spring-loaded. Ties would likely work for awhile, may even work long-term, but there is a risk profile that makes them a poor solution.
 
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While theoretically true, I've used nuts an bolts in a crunch on a MacMini2,1 CPU heatsink that ended up lasting years with no ill effects. Often, the springs used are so flimsy that I doubt they provide any tension at all anyway. The need hasn't arisen where I need to use zip ties yet, but I wouldn't hesitate to try.
 
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