What kind of problems can leaking capacitors cause?

Question

I inherited a faulty iMac G5 from a family member.  It would not boot up and the service center that dealt with it said the hard drive was bad.  It was still functional enough to extract valuable data from it, though.  I surmised that it wasn't really "bad"... just suffering from some damaged system files or directory structure.
With all valuable data copied off of the drive, I figured it would be best to completely wipe it and install fresh.  However, during the process the system would crash before installation completed.  In a few cases that I tried this, I could boot off of the 2nd DVD and actually interface with the system.  But, any running of the Disk Utility on the internal HDD volume would trigger a crash.  Running "fsck -fy" in single user mode would reveal errors, but the system couldn't fix them all.  And then at some points, I couldn't even get single user mode to work without crashing.
Long story short, I tested out the install with just one memory DIMM installed in slot 0, and found that it worked a little better with one of the DIMMs.  I was able to run another erase/install again.  FINALLY, the computer is working OK without crashes.
However, in doing this whole troubleshooting adventure, I noticed that a number of capacitors (maybe 5 or 6) are leaking slightly from the top.  You can see a tiny dollup of beige powder in the middle of the vent lines on top .  I read up on faulty capacitors and they can cause voltage fluctuations seemingly at random.  And this can wreak havoc on hardware.
So... I need to isolate this down a bit.  I ran the disk utility and the HDD checks out fine now.  If it was wearing out, wouldn't it continue to show up as faulty?  I'm starting to wonder if a coincidence of capacitor issues caused bad data to get written to the hard drive and screw it up.  Also, I'm wondering if any of the faulty capacitors could be in the circuitry path of the memory, that might cause it to experience subtle flaws and introduce errors... or even become damaged.
Lastly, any leaking capacitors means that they should be replaced and that it may be a gamble as to how long they'll continue to work before more serious problems arise.  Is there any rule of thumb about this where the G5 is concerned?  If the leaking is minor and no bulging of the capacitors is evident, might the computer work fine for a while, at least a few months until I'm able to embark on a capacitor refresh project?
Thanks for any relevant advice.

Answer 1

It's not worthwhile investing too much time or money in one of these. I had 3 logic boards replaced by Apple, all of which failed because they used refurbished boards, either with the same bad caps or boards that had been lying around for ages where the replaced caps slowly went bad over time from not having been formed. In fact, replacing the caps with known good ones would have been preferable to getting a replacement board from Apple.
The last board was the coup de grace, with the video chip failing -- another common issue with these turkeys.
My guess is the memory slot might be bad or that module. I've never heard of the caps fouling that part of the computer. But that's just my guess. I'd just keep using it until it dies, but I would be sure to have a backup (a bootable clone would be my preference) on an external drive so you don't lose all your data if and when it suddenly goes out.
But caps are relatively cheap and if you have the time, the expertise and the confidence....
See Spudnuty's posts on caps. He hasn't been around in a while, but he was the resident guru on fixing these things with bad caps. He did that all the time, but the video chip failure is probably insurmountable.
https://discussions.apple.com/message/11897383#11897383
https://discussions.apple.com/thread/2287036?threadID=2287036&tstart=0
https://discussions.apple.com/message/11513969?messageID=11513969#11513969