Cooling 43 Be primed for success when replacing water pumps With water pumps increasingly driven by timing control systems rather than the auxiliary system, Dayco UK’s National Technical Manager, Glen Goldstone, shares key points and best-practice advice to ensure the process of replacing them is a complete success. On removal of an existing pump, all the old coolant should be drained and the system flushed to remove any debris before being replaced with the vehicle manufacturer’s (VM’s) specified coolant, mixed with deionised water (not ordinary tap water), in the correct ratio. In common with both timing and auxiliary belt replacement, installation of the new water pump must be done following the VM’s stated process, with the pump’s gasket fitted correctly, without using any sealant, unless it is stipulated and then only using the correct formulation and in the quantity the VM indicates. In addition, before installation, the mating surface of the engine must be clean and free from debris. Before a pump is installed, it must be primed with coolant, but the pulley should not be rotated beforehand, and then once primed, only in the correct direction. Then care must be taken to ensure there is no misalignment, and, when in place, the free movement of the pulley should be checked before being tightened. It is vital that the correct VM’s tightening procedure is followed and the torque values are respected, because failure to follow the precise installation procedure can lead to a number of issues, including in the timing belt system, risking damage to the engine. In addition, if the pump is not evenly fastened, its flange can become distorted or break, and the gasket can leak. It is also important not to overlook the VM’s coolant installation procedure, which may stipulate the use of specific tools, such as a vacuum bleeding tool, to make sure the correct amount of coolant is pushed into the system. Once the system is full, it should be bled/purged to eliminate air bubbles or air pockets because an air pocket trapped behind the pump or air bubbles trapped inside its impeller chamber can affect the pump’s dynamic seal, causing premature wear and leading to coolant leaks and ultimately bearing failure. For more modern vehicles, the cooling system could consist of multiple water pumps, both mechanical and electrical, with the further addition of electrical one-way valves. In these applications, once the system has been sealed and the new coolant added, the vehicle should be connected to a suitable diagnostic tool, and the system can then be purged electronically. In some cases, more modern water pump construction includes coolantblocking shields designed to allow the engine to heat up quickly after start-up. This type of pump will utilise internal moving components, cavities and solenoid valves that can become contaminated and blocked if unclean coolant is re-used or if the system is not purged correctly. To help independent workshops ensure a best-practice replacement that avoids comebacks, Dayco offers its OE products as complete kits for many popular applications, ensuring that all the parts and accessories necessary to perform a full and successful job are included in the box. While products in Dayco’s wide range of timing belt kits are referenced as KTB (timing belt kit) and KTBWP (timing belt kits, complete with water pump). www.dayco.com This water pump failed due to a compromised O-ring seal and a misaligned timing belt. The failure of this water pump was caused by just tap water being used in the cooling system.
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