Hot water radiant heat is one of the oldest heating methods for residential homes. It works by heating water in a boiler and circulating that hot water through radiators in the home, thereby transferring the heat. The circulator pump is very reliable, but requires some basic maintenance to keep everything running smoothly. Newer pumps such as the versions manufactured by Taco are very low-maintenance, needing no oil and having no coupling to replace between the motor and the pump. Older style pumps such as Bell & Gossett require oil and some light maintenance.
Check which kind of circulator pump you have. See if it has any oil ports. Large B&G pumps take oil at the pump and motor bearings. These are located at the top of the pump. The motor bearing oil ports are at the far end of the pump away from the water pipe, and in the middle of the pump. The pump bearing oil port is located near the water pipe. Each port should be oiled with eight to 10 drops of non-detergent oil at the beginning of each heating season.
Use a rag to wipe away dirt, dust and oil from the pump. A large amount of oil on the bottom of the pump indicates over-oiling.
Inspect the bearing assembly between the motor and the pump. This is a set of two shaft couplings with springs between them. If the springs are fatigued, you will notice excess noise when the pump is running. These motor couplings can be replaced by loosening the set screws on each side with an Allen wrench and removing the four screws that hold the motor to the bearing assembly.
Inspect the end of the motor at the rubber motor mount. If the motor mount becomes U-shaped, this will cause undue stress on the motor and pump. It may also cause extra noise when the pump is running. The motor can be replaced by loosening the set screw on the motor side of the bearing assembly and removing the four screws that hold the motor to the bearing assembly.
Make sure there is water in the system before running the pump. Add water, if necessary, at the fill valve to the boiler. Bleed the air out of the radiators. Air in the system will cause a gurgling sound when the pump is running, and some areas of the house may not heat properly.