The best is to replace the thermal pads to avoid excessive overheating of the processor and graphic chip. You'll have peace of mind. You may use thermal pads or artic silver thermal paste available in any electronic shop. Also, just one advice, don't put too much pressure when screwing the two mounting bolts with springs on the heatsink. I use a 5/32" socket to do it. The mounting male part is soldered to the logic board and it's easy to desolder it if excessive force is applied when screwing. Other screws on the heatsink can be tightened without problem.

[quote|lemerise]The best is to replace the thermal pads to avoid excessive overheating of the processor and graphic chip. You'll have peace of mind. You may use thermal pads or artic silver thermal paste available in any electronic shop. Also, just one advice, don't put too much pressure when screwing the two mounting bolts with springs on the heatsink. I use a 5/32" socket to do it. The mounting male part is soldered to the logic board and it's easy to desolder it if excessive force is applied when screwing. Other screws on the heatsink can be tightened without problem.[/quote]

Thanks Lemerise, I bought some Arctic Silver 5 and the associated cleaning fluids thinking this would be the way on. However, looking at the pads they seem to be of different thickness - is it ok to use thermal paste at all three chips?

[quote|macmasher]Thanks Lemerise, I bought some Arctic Silver 5 and the associated cleaning fluids thinking this would be the way on. However, looking at the pads they seem to be of different thickness - is it ok to use thermal paste at all three chips?[/quote]

yes. Clean the processor, the graphic chip and the heatsink with the cleaning fluid and apply the thermal paste over the processor and the graphic chip (not to the heatsink). Spread a good coat of thermal paste with your finger but not too much then align carefuly the heatsink over them. Your guides are the screws holes. Try to not move the heatsink while you're fixing the screws.

[quote|lemerise]yes. Clean the processor, the graphic chip and the heatsink with the cleaning fluid and apply the thermal paste over the processor and the graphic chip (not to the heatsink). Spread a good coat of thermal paste with your finger but not too much then align carefuly the heatsink over them. Your guides are the screws holes. Try to not move the heatsink while you're fixing the screws.[/quote]

Just to let you know, my Mac is now up and running fine. A word of warning though for anyone attempting to use a thermal paste as opposed to the thermal pads which were originally fitted. Trial fit the heatsink onto the logic board first. On my G4 there was a small visible gap between graphic chip and the heatsink, the gap is easily taken up by the thermal pad but if you used a thermal paste only I don't think it would bridge it, or you would have to use a lot of paste which is not how its supposed to work. Just my experience.

[quote|macmasher]Just to let you know, my Mac is now up and running fine. A word of warning though for anyone attempting to use a thermal paste as opposed to the thermal pads which were originally fitted. Trial fit the heatsink onto the logic board first. On my G4 there was a small visible gap between graphic chip and the heatsink, the gap is easily taken up by the thermal pad but if you used a thermal paste only I don't think it would bridge it, or you would have to use a lot of paste which is not how its supposed to work. Just my experience.[/quote]