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can replacing heatsink & sensor solve sudden heat shutdown?

Recently got a nice MBP 2.0 core duo that only needed a new HD, but suffers from shutdowns when processors pegged- noticed in Handbrake, confirmed by running yes in terminal- SMC fan controller a little help, but still shuts down. Lost cause? I'm going to try the redo thermal paste fix, thought I'd replace heat sink and sensor, have read that sensor wire can get baked- anyone know of any success trying this?

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I would definitely try redoing the thermal paste but am not sure about the sensor. You might try one of those laptop stands with a fan in it. I had to use one on an HP laptop and it did the trick. Ralph

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Hi Machead -

Have you run (or have access to) the Apple Service Diagnostics 3S108 disc or EFI boot? I was having a similar issue with 2 different A1150's...

The ASD software pointed out a failing sensor (not every time, intermittently) on one MBP CD, and a failing GPU on the other. For whatever reason (never determined precise cause), the 2nd model's graphics chip kept getting really hot (even with either the SMC Fan Control App or the Fan Control Preferencepane). If you read up on the Core Duo generations' CPU and GPU chipsets, they are known to overheat (the industry measured percentage is in the high 30's). I had the same GPU overheat issues with an iMac of the same generation of chips: (T2400, T2500, T2600) & (ATI & ATI Mobility - Radeon X1600).

My solution for the first was to replace both sensors with known working sensors... worked great. Pretty straight forward repair.

My solution for the second took a bit more effort. I did this procedure twice... the solution "took" after the second attempt and it runs fine now. Essentially, without going into the complete disassembly procedure... I removed EVERYTHING (cables, sensors, pcb's - logic & DC-in, you name it). Cleaned everything thoroughly using canned air (fans & case), q-tips, electronics anti-static brush and high grade ethanol. For you, the key I believe is the fans, the venting, the heatsink, areas under the heatsink and fans. Those are the parts you really have to actually remove and clean (do not use anything but quality ethanol on circuit board or chipsets, canned air on the fans and maybe q-tip if you want to be extra thorough). I just removed everything to be thorough and give it a solid cleaning. Heat comes from multiple sites in the laptop, and reducing the overall heat was my goal.

The followup to the good cleaning was using a high-quality high-heat tolerant thermal paste. The cheap stuff is a blend of ceramic and silicon (great for some things - not for this repair, though)... the more expensive blends are polysynthetic silver (a few other types too). I personally find the Artic Silver 5 to be the most tolerant of high heat in tight spaces, but USE SPARINGLY. One dot (perhaps 2-3mm diameter) of perhaps (guessing) .15 cc's per heatsink pad.

To recap... I cleaned components listed and replaced the thermal paste twice. The first time improved lagging performance (from heat) and the frequency of shutdowns, but the problem didn't go away. The second time solved the problem. I still run the Fan Control PreferencePane as a safe measure (bumped up base speed of 1000rpm to 1500pm and kept temp tolerance range at 40-70).

Questions? Need ASD?

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I have the same model and after a number of logic boards and pretty much everything else during the warranty period, the overheating continues. It got really bad during the 10.6 install - system actually hit the hard temperature limit and shut down.

Since the warranty was up, I decided to open the thing up and see what I could do as far as removing 4+ years of dust. There wasn't much in there. I then decided to replace the heatsink compound. What was there was a bit excessive - it oozed well beyond the chips. I cleaned both surfaces then applied new (although not high quality) paste with a bit more restraint than the repair depot folks did.

It got a bit better, but any cpu-intensive task (for example, HD Netflix) would eventually bring the temperature to the 210F shutdown point. Further experimentation showed that basically anything that pegged the CPUs would result in both fans going to their max RPM (somewhere around 6000) but the temperature would eventually reach the shutdown point. I watched the CPU temp and various sensor temperatures with istat, Temperature Monitor, and a few other utilities. It seems like the sensors are all reporting correctly but the heat simply is not transferring from the CPU to the heatsink very well. CoolBook is the only thing keeping this thing vaguely usable. It's odd OS-X does not actually try to clock down the CPU as the temperature hits 200F or more though.

Anyhow, my next theory is that I'm basically dealing with a flawed design. If you compare how the heatsink is secured in the non-unibody MBPs to the unibody models, you can see a very big change. The old MBPs simply "sandwich" the heatsink between the mounting standoffs of the bottom case and the mainboard. On the unibody MBPs, there are springs involved the ensure that the heatsink is firmly seated against the chips. Given the amount of flex in the old MBP bodies, I'm beginning to think that the heatsink is simply not making firm, constant contact with the chips. I'd really, really love to see one of the ifixit crew look at this - it would be awesome to actually find the root cause of this all too common issue.

My next step is to try and find something that I can epoxy to the bottom case under each chip that can apply pressure to the heatsink to try and get a more solid bond between the chips and the heatsink. It sounds nuts, but I've got a few ideas swirling around... Any feedback would be welcome. I'm not ready to ditch this laptop until there's a truly hackintosh-friendly laptop.

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