They don't have to bulge or leak. They just dry out and don't perform their job anymore.
If you have capacitors with green writing on it then believe me, they are broken.
I have replaced the capacitors on 11 Amiga 4000 motherboards now and not a single one had green capacitors that were OK. Some didn't even look like they had leaked but snapped right off after applying some preasure because the pins had corroded underneath the capacitor.
So in short. ALL Amiga 4000 need repairs.