What mac pro 2008 do you have?
What processors is in it? If you got the 3.2 GHz ones, there are some hazard special cooling compound applied to the heatsinks.
This need to be removed with care if needed. Use gloves!!
All this is written in the service manual, only available to Staff members at apple service centers.
The 3.0 GHz or 2.8 uses a piece of silver pads, this will melt and act as cooling compound.
Be careful when remove!
Today is 2011. The cooling compound is 3 or 4 years old, and pretty likely dry as old bubblegum, this should be changed at least once a year.
Get you some Artic silver S5 at a PC hardware store, costs about ten bucks.
If they don't have it in stock. Ask for Artic silver Céramique 2 or visit some other PC hardware store.
Artic silver S5 can move high temperature as 8,9 W/(m*K).
Other cooling compounds only moves 2 W/(m*K).
Get your hand on a brush for painting, this you will clean internal parts with.
Don't use compressed air ever.
Before doing anything, try to look and understand how to disassemble your mac pro, to get it clean.
http://www.youtube.com/watch?v=xOF435jCg8E
I know it's in german. I understand..kind of nothing of what he is talking about. But hey, just fallow he's steps in the video and you will be fine.
"Why not use compressed air?"
Because if you apply compressed air, you will loosen the dust.
When the fans spin again, the dust just a moment ago was flying around now flying deeper in to the heatsink. Making the heatsink to clog even more and more for each time you use your mac.
With your brush, clean all the internal parts. Including fans, heatsinks (if they are clogged, blow from the back to forth until you can see trough clearly).
Now grab some rubbing alcohol. Take the CPU's out of their sockets.
BE CAREFUL!, don't touch the contacts underneath.
Rub of the old cooling compound of as good as you can.
Please do the same to the heatsinks.
You might find your paper now being black. This is good.
This means dirt is being removed.
Re-seat the CPU's carefully in to their sockets. Close the latch.
Now grab your Artic silver S5 and apply just a little at the CPU's
Try to spread the compound to the whole surface, you
might need to apply some more. Now apply some on the heatsinks.
Spread it just like on the CPU's.
Attach the heatsinks one by one. Remove each to check that compund has
spread to the whole surface before screwing the heatsinks to it's place.
Don't forget to put the Temperature sensors back in to place!!
And your done!
Now disassemble your GPU card, on these there are only cooling pads.
What they are made of is simply wax. And all this has with the time dried out.
Clean the heatsink and use again, rubbing alcohol cleaning the old compound of.
When taken a part, if there are differences in levels on memory parts and the cooling compound wont reach the heatsink when putting it all together.
Cut some small pieces of copper plate and apply all around as many until the level is just perfect to to make contact to the surface of the heatsink. Now apply cooling compound on both sides of the copper plate. Make sure that no part has no cooling compound.
WARNING!! When cutting the copper plate. Make sure, not to make the pieces to big to short other components. The copper plate should only cover memory components and voltage regulators where heat comes of.
Try to make them as identical as the old cooling pads, this will make sure that the copper plate is seated where it should be.
Now put the GPU card together.
Now on to the next thing. Your PSU.
Grab a flashlight. Take out the PSU and look in to the grill.
See if you notice any loose internal cables.
Anything not attached properly.
If it is just clogged with dust, take it apart and clean it.
When taken apart, and you discover something not securely is sitting tight.
Are your soldering skills good, unsolder the component and reattach it again.
Other ways visit an electrician at any repair center. Don't need to be an apple repair center because the PSU has nothing with apple to do.
It's just supplies the mac with power.
If you can't see any bad components but you still worried, just visit an electrician just to be sure.
If the noise is not hazard loud and seems dangerous. Now put your mac together and see the temperatures drop.
Please ask if you need help. This is a mainly service needed to be made on every computer. Computers are not machines which work forever.
