Vacuum hose disconnected from power brake servo or power brake servo has failed diaphragm (very rare). Massive vacuum leak that causes inadequate vacuum for power brake assist. Air bubbles in in hydraulic lines. Disc brake calibers seized or dragging building up excessive heat (usually with visible smoke). This can lead to boiling of fluid and bubbles in hydraulics. That is about all I can come up with at the moment. Also I don’t see how the o2 sensor could be related but maybe something got disconnected (see above) and not hooked back up properly.
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Vacuum hose disconnected from power brake servo or power brake servo has failed diaphragm (very rare). Massive vacuum leak that causes inadequate vacuum for power brake assist. Air bubbles in hydraulic lines. Disc brake calibers seized or dragging building up excessive heat (usually with visible smoke). This can lead to boiling of fluid and bubbles in hydraulics. That is about all I can come up with at the moment. Also I don’t see how the o2 sensor could be related but maybe something got disconnected (see above) and not hooked back up properly.
Vacuum hose disconnected from power brake servo or power brake servo has failed diaphragm (very rare). Massive vacuum leak that causes inadequate vacuum for power brake assist. Air bubbles in in hydraulic lines. Disc brake calibers seized or dragging building up excessive heat (usually with visible smoke). This can lead to boiling of fluid and bubbles in hydraulics. That is about all I can come up with at the moment. Also I don’t see how the o2 sensor could be related but maybe something got disconnected (see above) and not hooked back up properly.