Intex outlines a few ways you can fix your 603 pool pump, if you notice leaking, if water starts to flow through the pump slowly or if air becomes trapped in the pump housing or inlet hose. These are common problems that Intex recommends most pool owners can fix on their own. If you experience problems outside of these, contact Intex directly before performing any further repairs. The company can provide more direction on how specifically to fix the pump and may even recommend replacing the unit entirely.
Check the filter cartridge for holes or dirt buildup if the filter doesn't clean the water well, if it pumps the water slowly or if the top cover starts to leak. Unscrew the pool inlet nozzle and strainer grids and insert the included plugs. Twist off the threaded cover and cover seal in a counterclockwise motion. Remove the old filter cartridge. Replace with the new cartridge and replace the connections and covers.
Pull out the intake hose and discharge it into the pool to clear obstructions, if the filter pumps water slowly.
Reinstall and tighten the hose clamps, nozzle and strainer if you notice leaking or if the water flow is slow. Insert the nozzle in the upper position of the pool inlet and the strainer in the lower position.
Open the air release valve, if air becoming trapped in the pump housing and the inlet hose is the problem. Lift up and then lower the inlet hose until water starts to flow from the air release valve.