|
How To Replace A Water Pump |
|
There are a lot of mis-conceptions regarding water pump replacement. Before attempting to replace a water pump, make sure that the pump is the cause of your problem. If the engine is over-heating it is usually a result of low coolant level which could be caused by a leaking hose, gasket, radiator or the water pump. A defective thermostat is the most common cause of engine overheating but this condition will not necessarily cause a coolant leak unless the engine is operated beyond the maximum operating temperature which will force coolant past the pressure cap and out the overflow hose or tube. A defective thermostat will cause the engine to overheat within a few minutes from a cold start. The best method of determining a coolant leak is to pressurize the cooling system with a hand operated pump which is attached to where the pressure cap is removed. The pump will have a pressure gage attached. It is important not to exceed the normal operating pressure of the cooling system which is usually marked on the pressure cap. This test should be performed without the engine running. If the leak is significant, you will soon notice coolant dripping on the floor and in severe cases the coolant will even spray from the point of the leak. A leaking water pump is usually the result of a worn out pump shaft bearing which will cause the seal to leak. If the bearing is extremely worn, there will be noise and looseness of the pump drive pulley which can be detected by applying sideways force on the pulley. Most water pumps have a "weep" hole in the pump casting, and if coolant is leaking from that hole, the pump definitely should be replaced. In very rare cases, the water pump impeller will become disengaged from the pump shaft and the only way to determine this condition is to remove the pump. If it is determined that the water pump is the cause of the problem, replacement of the pump can be relatively simple process or it can be very involved, depending on the type of engine you are working on. Most of the older engines previous to the overhead cam engines that utilize a timing belt had the water pump attached to the front of the engine in plain sight. The cooling fan blade was usually attached to the water pump shaft. Pump replacement could be accomplished by removing the necessary engine accessories such as the alternator, power-steering pump, and in some cases the air- conditioner compressor. Usually these accessories can moved out of the way enough to gain access to the pump without removing them completely from the vehicle. At that point the pump can be detached from the block and the new pump installed. There is one important tip that I must mention. Take extreme care to remove all of the old gasket material from the engine and make sure that the new gasket or gaskets are in place. This can be accomplished by "gluing" the gasket to either the block or the pump (not both sides) or by using a couple of guide bolts to align the pump with the block. If your engine has the pump located behind the timing cover, and if the pump acts as an idler pulley for the timing belt, do not attempt this procedure unless you are very knowledgeable and have done this before. It requires correct alignment of the timing marks on the camshaft or camshafts, crankshaft, and in some cases balance shafts and oil pump. If you mess up, severe engine damage can be a result. After the pump is installed and all of the hoses are connected and the accessories are re-attached, fill the cooling system with as much coolant as you can get in the system. Do not start the engine at this point. It is critical to "bleed" the air from the system. A pocket of air in the engine block or cylinder heads can cause real problems. Most shops have a bleeding pump to perform this procedure, but if you do not have access to this equipment, it can be accomplished by loosening a heater hose a heater hose where it attaches to the engine and allowing air to escape until coolant appears. This may take more than one attempt. Some engines do have a bleeder valve or screw, usually on or near the thermostat housing. Always install new coolant when replacing a water pump. Proper belt tension is also very important. Too much tension on the drive belt can cause pre-mature pump shaft bearing failure. After a few skinned knuckles and many expletives, you should be ready for a test drive. Happy motoring! |