Well, I've got the new Mac 5500 flashed to PC, so I removed the stock heatsinks today in preparation for the Zalman sinks. I have a pair each of the 32mm and 47mm Zalman's, and after some test-fitting and deliberation I've decided to go for the 32mm sinks after all.
My case setup for this system leaves me with enough room for the 47mm sinks, and they are a nice blue that matches the sinks I plan to put on the RAM. However, with that 120mm fan blowing half-under, half-over the card, I believe the 32mm sinks will be adequate cooling, and they leave me with one more usable PCI slot "just in case". I also have an idea that they actually have almost the same surface area as the 47mm sinks, because there is an extra row of fins in each direction. Finally, if I ever do need to put 40mm fans directly on the heatsinks, it will be much simpler with the flat-topped 32mm sinks.
I had something of an epiphany while removing the stock heatsinks this time around, too. Last time I flipped the card so the coolers were facing down, then slipped drops of acetone onto the heatsinks where they adhered to the chips (using a makeshift pipette). After doing that several times, I tried the freezing trick and worked a blade into the crack between the actual chip and the heatsink, and pried that way... with disastrous results.
This time I repeated the acetone procedure (once the sinks come off you can see that it eats into the adhesive a couple of mm on all sides, weakening the bond by maybe 10-15% based on area), then the freezing trick. Instead of a blade, I tried just prying with a credit card (saw that suggestion somewhere here), but it didn't provide enough force to do the job without some scary flexing.
So then I thought, hey, what if I cut that card up (it was an expired card) and use it to
protect the card while I pried with something stiffer?
I cut the card into some strips of different size and slipped them between the base of the chip and the heatsink. They were quite loose like this, but I overlapped the corners and pushed a double layer in there, which was nice and snug. Here's a picture of what I mean (sorry, the heatsinks are already off, but you'll get the idea anyway):
3MB ImageAt this point there was basically no way the heatsink could damage anything on the card when it came free,
and I had a perfect base to pry on with a nice dull flat-head screwdriver! After re-freezing the card, I just slipped the screwdriver in on top of the credit card on the PCI connector edge, and pried up gently. The credit card protected the base of the chip (that fragile PCB portion) from being crimped, so I could use much more force without feeling out of control.
*crack*
The heatsinks just popped loose like a charm. After all the time I spent messing with it, once I discovered the secret it took all of 5 minutes to get both sinks off with no risk of damage (unless of course the heatspreader on the chip had pulled off instead, but they seem to be awfully strong).
Anyone who plans to do a cooling mod on a V3, V4, or V5 with the glued stock heatsinks should
definitely attack it this way. It sure takes the worry out of the procedure.