We’ve all come to expect that various components on our classic cars require routine maintenance, but on early classic cars the maintenance schedule includes several items we’ve come to take for granted on more modern classics. One item that requires more care on older classics is the water pump. These early water pumps worked well but to create a watertight seal on the impeller shaft, packing material is used. This material requires the packing nut on the water pump to be periodically tightened to seal the shaft and in time the packing will need to be replaced.
The water pump on your classic car is a relatively simple centrifugal pump driven by a belt connected to the crankshaft, and it serves to circulate coolant while the engine is running. The pump then circulates the coolant from the pump to the engine block and head then returns the coolant to the radiator then finally back to the water pump. The most common weak links in the system are the thermostat and the water pump as they have the only moving parts. More modern style water pumps use seals on the impeller shaft as opposed to packing, but in time even these fail but are not readily serviceable by most enthusiasts. This requires simply having the pump professionally rebuilt or purchasing a new/rebuilt pump.
For owners of older classic cars it is important to understand how to properly adjust the water pump packing nut and replace the packing. Mark Simpson explains what water pump packing is and the process of replacing the packing. Simpson also discusses the process of adjusting the packing nut for both recently repacked pumps or as part or your regular maintenance schedule. On most cars these early water pumps are designed to run for years, but with a little service you’ll have them running trouble free as well.