Timing belt failure investigated by Gates

Gates has investigated the cause of premature timing belt failure in the Synchronous Belt Drive System (SBDS) for number of Ford, Peugeot and Citroen models with 1.6L petrol and PSA diesel engines.

The vehicles, all of different years, include the Ford C-Max, Fiesta and Fusion; the Peugeot 206, 207, 307, 308, 407, Expert and Partner; and the Citroen C3, C4, C5, Berlingo and Jumpy.

Modern cooling system hoses do much more than circulate coolant from the radiator to the engine and back. With technological advances moving so quickly, if a model has not been seen in the workshop for a while, years of mechanical repair experience may deceive. Installer errors are common.

Analysis of claims data showed that within this group of vehicles, a small number of premature belt failures had occurred soon after each of the timing belt kits were installed. In each of these vehicles, water leaks had been identified as the cause.

The most frequent causes of water pump failure usually occur as a result of weep hole leakage, leakage from the mounting surface, rust and corrosion, deposit build-up, cavitation, damaged bearing, damaged or broken shaft, use of inappropriate coolant and dry run mechanical seal (water pump).

Gates recommends replacing the water pump at every scheduled belt change. A leaking water pump inevitably has an adverse effect on the belt and tensioner. Investigations confirmed that, while fitting errors had taken place in some cases, in the others, fitting procedures had been followed to the letter.

When timing belt replacement involves the installation of a water pump, technicians have a range of associated fitting issues to consider. Many of the latest cooling system hoses ‘branch off’ to serve various components, and they typically feature connectors and sensors.

The common causes of hose failure are:

  • High temperatures and prolonged exposure to fluids – this causes the rubber to become soft and expand
  • Engine vibration and stress from circulating coolant – this causes plastic connectors to become brittle and susceptible to breakage
  • Hose removal – this sometimes causes quick connectors to fail when removed for maintenance
  • Disconnecting sensors from hose assemblies – this increases potential for damage
  • Flow restrictor and directional valve locking – these control the flow of the coolant and can become locked open or closed. If the coolant is not getting to the radiator or engine, it is likely that something is locked inside the hose.

If a water leak reaches the belt, premature failure of the SBDS system becomes inevitable, and failure of the engine is a likely consequence. The Gates investigation found that there was a common cause for these problems. The cause was found not to be the water pumps themselves, but the coolant hoses that connect them.

Coolant hoses have become more complex in recent years; more and more are application-specific and use a variety of materials. The coolant hoses on these particular engines (OE part numbers PSA – 1336.X3 and Ford – 1230674) are made of plastic, and so are the connectors.

Detailed analysis confirmed that hostile conditions inside the engine cause the plastic to become brittle over time. Investigators found that it was easy to damage the connector or cause an unseen fracture in the plastic pipe by simply removing the hose to replace an old water pump or replacing the hose following fitment.

As removal and installation procedures require handling of both the water pump and the modular hose assembly, Gates recommends a thorough check of the modular coolant hose and plastic connectors for signs of damage whenever removing and installing a timing belt kit and water pump to (PSA) 1.6L diesel engines.

Furthermore, it is recommended that technicians install a new modular hose assembly (such as Gates 02-1730) whenever a new water pump kit (Gates KP15598XS, KP15656XS, KP15688XS, KP25598XS) is fitted to any of the aforementioned Ford, Citroen and Peugeot models.

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