T60 GPU overheats when doing 3D graphics

[RaviN]

T60 8755, 2GB RAM, XP SP3, running TPFanControl. The computer is out of warranty.

I replaced the fan assembly in my T60 a couple of days ago. I ran PC Doctor 5 to ensure I didn't damage anything during the installation. When the 3D graphics test ran, the GPU temperature shot up from mid-60 deg C to > 100 deg C. I stopped the test immediately. I downloaded a 3D benchmark called Furmark along with a 3D game called gltron and saw the same thing. Normal graphics, video, etc. don't cause the spike, only the 3D codes. The new fan kicks into its highest speed and the GPU gets back down to normal temperatures quickly after stopping the 3D-intensive work. The CPU temperature and other monitor points look the same as before.

Is this a common problem with the T60 or did I bork the fan installation? The fan came with thermal grease for the CPU and the conductive pads for the GPU and the other chip close to the GPU. Unfortunately, I did not do any of these tests before replacing the fan. The old one cooled well but had begun to grind and the noise was bad.

[Harryc]

Those GPU temps are too high, particularly if it appeared that the were about to go higher if you did not stop the test. I'd guess that the thermal pad is not contacting the GPU or there is a bend or break in the heat-pipe going to the GPU. Do you see any dents in the pipe?. Lets also talk about FRU#'s. What FRU # fan was in the machine and what FRU# did you replace it with? One more thought...I've heard of some of the thermal pads coming with a plastic sheet over them to protect them from dirt in storage/shipment. It has to be removed before installation. Did yours have that sheet?

[RaviN]

Those GPU temps are too high, particularly if it appeared that the were about to go higher if you did not stop the test. I'd guess that the thermal pad is not contacting the GPU or there is a bend or break in the heat-pipe going to the GPU. Do you see any dents in the pipe?. Lets also talk about FRU#'s. What FRU # fan was in the machine and what FRU# did you replace it with? One more thought...I've heard of some of the thermal pads coming with a plastic sheet over them to protect them from dirt in storage/shipment. It has to be removed before installation. Did yours have that sheet?

I didn't note the replacement FRU but it looked identical to the one I took out. I'll check with the seller, who is a respected forum member and from whom I've bought other accessories before.

Good question re: the thermal pads... I did not notice, but I wasn't looking for, anything to peel off.

I'll disassemble the unit over the weekend and check for the items you mentioned.

By the way, do you mean mid-60 deg C GPU temps are too high or the >100 deg C? This machine has always shown GPU temps of 65-75 deg C in normal operation, depending on how much conventional video I had up.

EDIT: The old fan (by inspection) and the new one (per the seller) are the same FRU# 41W6409

[Harryc]

65*C is normal for a T60 GPU at idle. I'd expect no higher than 85-90*C under full load.

[RaviN]

I think the problem is solved for now.

1) Taking out the new fan assembly, I noted uneven indentation on the thermal pad to the GPU. The heatpipes showed no obvious damange
2) I reinstalled the assembly and tried to keep even pressure across the screws

Result: Overheating on Furmark and PC-Doctor 5 3D benchmarks, but, rise times were much longer. The PC-Doctor 5 lighting and transformation test had the GPU peak at 100*C after a gradual rise. The test completed. Previously the temperature spiked almost immediately to >100*C and I stopped the testing

3) I put in one of the thermal pads from the old fan assembly between the top of the heatsink and the retaining bracket. Incidentally, a plastic film came off of this pad when I took it off. I left it off and used the waxy material as a shim. I did not disassemble the new fan to take the film off.

Result: I ran Furmark for over 12 minutes and the GPU leveled off at 80*C. The fan could keep it equilibrated at one of the lower fan levels (1 or 2). The soft shimming action of the old thermal pad has, I think, put the right amount of pressure across the GPU.

The CPU is running hotter than before, though. I think this is due to reusing the thermal compound. It has not gone over 60*C so I'll probably leave things as they are for now.

I am watching a high-definition concert broadcast at near full-screen. CPU is at 60*C at >60% load on both cores at 2GHz and the GPU has been stable at 67*C. Fan level is 1 and slightly below 3000RPM.

Thanks, HarryC, for the tips.