How does a capacitor fail ?

Electrical symptoms

As an electrolytic capacitor ages, its <a href="https://en.wikipedia.org/wiki/Capacitance" target="_blank" rel="nofollow noopener noreferrer">Capacitance</a> usually decreases and its <a href="https://en.wikipedia.org/wiki/Equivalent_series_resistance" target="_blank" rel="nofollow noopener noreferrer">Equivalent Series Resistance</a> (ESR) usually increases. The capacitance may abnormally degrade to as low as 4% of the original value, as opposed to an expected 50% capacity degradation over the normal life span of the component. When this happens, the capacitors no longer adequately serve their purpose of filtering the <a href="https://en.wikipedia.org/wiki/Direct_current" target="_blank" rel="nofollow noopener noreferrer">Direct current - Wikipedia</a> <a href="https://en.wikipedia.org/wiki/Voltage" target="_blank" rel="nofollow noopener noreferrer">Voltage</a>on the motherboard, and a result of this failure is an increase in the ripple voltage that the capacitor is supposed to filter out. This results in a system instability. Capacitors with high ESR and low capacitance can make power supplies malfunction, sometimes causing further circuit damage. In computers, <a href="https://en.wikipedia.org/wiki/CPU_core_voltage" target="_blank" rel="nofollow noopener noreferrer">Cpu Core Voltage</a> or other system voltages may fluctuate or go out of range, possibly with an increase in CPU temperature as the core voltage rises.

Source <a href="https://en.wikipedia.org/wiki/Capacitor_plague" target="_blank" rel="nofollow noopener noreferrer">Capacitor Plague</a>

All the electrolytes are similar to rechargeable batteries as more and more cycles are done with the capacitors electrolyte losses its original property and increases its internal resistance

This effect is similar to settled water and stirred water having lots of impurities