Grease the bearings regularly
Lubricating and inspecting the bearings in your swamp cooler or evaporative cooler can save you a lot of headaches and expense. In most commonly used coolers, greasing the bearings is a very simple job. Most residential and small commercial models originally come with a bronze bearing. There are no moving parts in these bearings, as with ball bearings. Bronze bearings are made with a bronze sleeve inside a die-cast steel housing. The fan shaft rotates inside the bronze sleeve. These types of bearings allow smooth, low-friction movement between the two solid surfaces. The bronze portion of the bearing is generally about 1/8 to 3/16 inch thick and is porous for continuous lubrication. You will see a cup of oil on top of the bearing. Open the cup, and then drop about 5-10 drops of light machine oil into the oil tube. This should be done at least once a year for light cooler use, or several times a year for heavy use. Although bronze bearings are relatively inexpensive, they are quite durable. Often times, if you lubricate them regularly and the belt tension is maintained correctly, the bearings will last the life of your evaporative cooler.
Inspect your bearings
It is very important that you inspect the thickness of the brass sleeve when greasing the bearings. As I mentioned earlier, the bronze sleeve on the bearing is only 1/8 to 3/16 of an inch thick. The steel fan shaft rotates continuously within the bronze sleeve. If the steel shaft eventually wears through the bronze sleeve, then you have steel turning on steel. Steel spinning on steel always makes a loud, high-pitched noise somewhat similar to the sound of a loose belt squeak. Again, it is very important that you inspect the thickness of the brass sleeve. When any part of the bronze sleeve has worn to half its original thickness, the bearing should always be replaced. If you let the bearing get to the point where the steel rotates on the steel, you have damaged the blower shaft. When the shaft has been damaged, you will not be able to use a bronze bearing again. The rough shaft will wear out quickly through a new bronze bearing. At this point, I would recommend that you install a more expensive ball bearing with set screws in the inner race. This will bond the inner race of the bearing to the blower shaft and damage to the shaft will not cause any future problems. Also, if the ball bearing ever comes off, it will never damage the blower shaft.
Changing your cooler bearings
Unlike most other types of blower units, evaporative coolers continually produce moist air that creates rust on the bearings, blower shaft, and pulleys. This often makes it much more difficult to change the bearings. There are two things that I always recommend when changing cooler bearings. Use a penetrating solvent on any part that is rusted. This often happens on the pulley and shaft of the blower, as well as the inner race of a ball bearing and shaft. Even after using a penetrating solvent, I have sometimes had to use a pulley puller to remove the pulley from the blower. The other recommendation that is very important is that you should always sand the rust off the blower shaft before pulling on the blower pulley or bearing. If you don’t sand all the rust off the shaft, not only will you have trouble removing the pulley and bearing, but it will be very difficult to slide the new one onto the shaft. You may also be tempted to use a hammer to drive the new bearing in place, which can often damage the bearing. As you can see, a few pieces of sand cloth to sand the rust off the shaft will make the job much easier and actually save you time in the long run.