Electrolytic Capacitors consists of a solid Anode and a liquid cathode. The cathode is the liquid electrolyte. Sometimes, the electrolyte inside the capacitor evaporates causing the capacitor to fail.
The drying of the Electrolyte in the electrolytic capacitor can be due to age or high temperature. Hence, care should be taken to ensure that the capacitors are not operated at temperatures higher than the rated temperature.