Is it possible to remove air bubbles from inside a pH probe?

Air bubbles are normal in pH sensors and in some reference sensors. They are necessary because the pH sensor is a sealed device with no vent. Without the air bubbles the expansion and contraction of the liquid with temperature changes could cause the glass to break. 

We require that the pH and Reference sensors, or combination sensors, be installed with the tip pointing down at least 15 degrees below the horizon. If the tip is pointed up the air bubbles can migrate to the tip and keep the pH sensitive glass from making contact with the buffer solution inside the sensor. 

In addition to bubbles in the tip, air bubbles can get trapped in the electrolyte solution of the reference system. Some reference sensors use thickened KCL or gelled KCL. Some are packed with KCL crystals to create a saturated KCL solution. These air bubbles can cause unstable readings and may make it difficult or impossible to calibrate. In order to reduce or remove the air bubbles, hold the probe firmly by the cable and shake it so that the air bubbles move to the upper end of the probe. If air bubbles are trapped inside the solid KCl crystals, heat the electrode tip in warm water (max. 60°C). This will dissolve some of the crystals and allow the air bubbles to move. While the sensor is still hot, shake the probe as described above. Allow it to cool before reinstalling it in the process.