How do I check water pump ?

Thanks, I didn't have all the air out of cooling system after I got it out it didn't run hot. I used K&W, followed directions to the letter. Took out thermostat when running with K&W in cooling system. Flushed again, installed thermostat, and changed oil & filter. Changed oil again after flushing 2nd time. Doing again soon. Surprisingly it worked. No water in oil and not over heating. Radiator is doing ok. Have drove about 75 miles. I will keep close check on it. But you are right if the vehicle is worth keeping. This truck not by far. It been a reliable one.