Thermal compound breakdown?

pctech · Jun 05, 2011, 20:16:18

Was running speedfan earlier and found out my CPU core temp was 68C (max temp for a Presler Pentium D 68 I think)

Rebooted and went into the BIOS and brought up the hardware monitor, the CPU temp rose to 72 so I immediately shut down.

Unscrewed the side and found the innards had lots of dust, got the hoover out and very carefully moved the nozzle over the fans and boards.

Currently got the side off and temps are what I would expect to see (43C) but I did wonder whether it could be a sign that I need to renew the thermal compound?

The PC is five years old and I know its a pig of a job so really don't want to have to do it unless I need to.

Can anyone offer any opinions?

Steve · Jun 05, 2011, 20:20:00

Are all the fans working? Taking the side off is not always effective as it interrupts the airflow pathway. The 'in' filters at the front are often very dirty.

pctech · Jun 05, 2011, 20:25:27

front air intake (120 mm fan) is hoovered from front every week.

all fans are working,

I'll put the side back in a bit but just wanted to make sure the CPU was cooling down.

Steve · Jun 05, 2011, 22:02:30

Are there any foam filters near the front fan?

pctech · Jun 05, 2011, 22:09:01

Yes but the main HDD is mounted just behind it.

Just as an update, I replaced the side panel about 30 minutes ago and been keeping an eye on the temps in speedfan which appear to have normalised whereas they were into the 60s when just doing browsing and mail collection.

Fans sound as though they are running smoother too.

Lesson learned I think, hoover inside every couple of months.

pctech · Jun 05, 2011, 22:09:50

And need to make sure the new one is easy access too.

gizmo71 · Jun 05, 2011, 22:38:34

Yeah - dust is the enemy, thermal compound will outlast the CPU.

I did a post mortem on my mum's old PC last week - I'm amazed it could still boot, it was furrier than a wooly mammoth in a tumble drier!

pctech · Jun 06, 2011, 09:47:44

Big cases are great but they of course offer a lot of space for dust to collect in.

Just checking the temps again while browsing this morning before I head out to work and they are still normal so it does look like the problem is resolved.

I'll post a pic or two of the machine and its freshly dusted innards on Sunday.

D-Dan · Jun 06, 2011, 12:27:33

I clean mine by vacuuming maybe once every 8 - 9 weeks, and at 6 monthly intervals I remove the fans completely and clean both sides of the blades with a moist cotton bud (well, usually several cotton buds). Not only does it keep the fans effective but it also prolongs their life since it ensures that they don't become unbalanced with dust, thus increasing wear on the bearings.

Steve

Technical Ben · Jun 07, 2011, 22:43:53

Perhaps some dust got stuck on the fan? Was it running at speed, or slow?

pctech · Jun 07, 2011, 22:53:41

It's fur (geddit) to say quite a bit came out so I can only imagine it was sitting on top of the mesh over the processor on the heatsink just below the CPU fan.

At the time CPU fan rotation was recorded about 2524-2954 and is now a steady 2250 RPM with core temp at 39C.

zappaDPJ · Jun 07, 2011, 23:25:29

It's quite common, the norm in fact to find a carefully woven carpet sitting between the fan and the heat sink. As gizmo said earlier, thermal compound is likely to outlast the usefulness of a CPU.

In any case thermal compound doesn't really work in the way you'd think. It's actually somewhat detrimental to heat transfer. Ideally you want metal to metal contact but that's unlikely because even the best quality CPU die and heat sink will contain small pits in the metal. Thermal compound used properly simply fills in those pits, expels the air so the heat is transferred rather than leaving it trapped in air pockets.

Technical Ben · Jun 08, 2011, 11:51:10

I hope the Zalman fan I got solves half of the problem. The fan is in the middle, with the fins on the outside. The fins have all their edges accessible. So clearing dust of is one circular sweep.

The standard heatsink was square. The dust got caught in the tiny little slots and the centre. But the Zalman has no "choke" points for dust to hide in.

pctech · Jun 08, 2011, 14:25:22

When I get my next system built I am going to spec something like a Zalman rather than the Intel stock cooler this one has not least to quieten it down a bit as at normal operating speed its not that quiet and when under load it sounds like its about to take off.