As most automotive professional technicians know, a vehicle’s timing chain synchronizes the rotation of the crankshaft and camshaft(s) ensuring proper timing and allows the engine’s valves to open and close during each cylinder’s firing. The timing chain components are internal engine components and require healthy oil feed for proper function, making oil maintenance very important. Timing chain systems are not scheduled maintenance items so repairing before catastrophic failure is key; therefore, it is important to be able to recognize the symptoms. Signs a timing chain needs to be replaced include:

• Later model variable valve timing (VVT) applications will trigger engine codes indicating failure to be able to fully control camshaft timing.
• A VVT system failing over time can develop engine rattles at start-up and/or in operation.

Signs of a Failing Timing Component or VVT Sprocket

There are a few signs that a technician may find that would indicate a timing system issue. The most obvious would be audible noise from the timing cover area during engine operation. This noise could be a temporary rattle at startup or a rattle throughout operation that changes with engine speed. Other signs can include poor engine performance or fuel efficiency, camshaft timing function engine codes, or timing chain guide debris found in the engine oil.

In some cases, timing chains stretch due to improper owner maintenance. Going too long between oil changes and using the wrong type or viscosity rated motor oil can cause the timing chain pins and plates to wear, resulting in timing chain stretch.

Timing chain noise is commonly most noticeable during cold startup of the vehicle when oil pressure and oil flow is at its lowest. In this situation, the lack of oil supply tests the actuators’ lockout pin function. When an actuator has very low or no oil supply, an internal pin locks the actuator into a solid state. Failure of this lockout pin can allow the sprocket to cycle back and forth with no restriction causing extreme instability in the chain system. The timing chain tensioners are also tested in cold start situations. The hydraulic tensioners contain check valves that are intended to keep the tensioners full of oil at all times. When a tensioner check valve becomes weak or fails, it will take some time after startup for the tensioners to build up adequate pressure to stabilize the chain.

The Ford 5.4-Liter Modular Engine

These characteristics apply to the Ford Modular engine. While system replacement in Ford Modular engines is not particularly difficult, the repair is timely and most of the labor hours for the service are spent removing the accessories, valve covers, and the timing cover. Based on one popular labor guide, timing system replacement in 3V 5.4L Ford F-150 trucks requires 11.8 hours of labor.

Having a thorough understanding of the timing and VVT systems in order to properly diagnose and repair engines the first time, avoiding that second 11.8 hour job, is crucial for automotive technicians.

Cam Journals and The Importance of Oil in Timing Chain Systems

Cam journals may also need to be inspected when there is evidence of unstable timing chain operation without a clear cause or reason. It is important to note that not all timing system repairs require cam journal wear inspection. Evidence of unstable operation includes severely worn or broken guides, prematurely worn or stretched chains, and/or audible noise from the timing chain area during operation. This instability can be caused by several reasons, including cylinder misfires, fatigued chains, VVT system component failure, or a lack of sufficient oil supply to the tensioners or VVT components.

Oil supply to the VVT actuators is where the camshaft journals come into play. The camshaft actuators in the Ford Modular engines are oil pressure-operated units. Oil from the engine’s oil pump flows through the engine and cylinder heads to the VVT solenoid valve bodies. The solenoids, using pulse width modulation from the engine’s management system, control the oil supply going to the actuators on each head. Flow is directed by the solenoids into one of two oil ports that supply oil to different sides of the VVT actuator rotor vanes, one to advance camshaft timing and one to retard camshaft timing. For the oil to reach the actuators from the solenoids it must travel through the front camshaft journals, into the camshafts, and then through the actuator bolts or directly into the actuators. Therefore, camshaft journal health is critical to actuator function. Wear to the journal can allow for oil crossflow, resulting in oil feed to the wrong port, or hemorrhaging of the oil feed all together resulting in improper or unstable phaser operation.

When unstable operation is coupled with failed timing or VVT components without clear cause, it is advised to check front camshaft journal wear. To check front journal wear, the camshafts must be removed, and the front camshaft caps must be reinstalled. Inspect the bores for deep scoring and wear, then use a bore mic to measure the journal bores. The camshaft journal outside diameter (OD) specification is 1.126” – 1.127”. A properly torqued camshaft journal bore should be within 1.128” – 1.129”, resulting in a journal OD to camshaft journal bore clearance of 0.001” – 0.003”. If the camshafts and journals are within this specification, reinstall the camshafts. The front cam journals also set the camshaft’s endplay, which is .001” – .007”. If you find that the camshaft journals are outside of these specifications, new cylinder heads are needed to ensure proper VVT system function.

Cloyes’ Solution

Traditionally known as a manufacturer and supplier of timing chain systems, Cloyes has developed a line of timing chain VVT kits to support its customers who conduct time-consuming replacements, such as on the Ford Modular 5.4-liter engine.

VVT components are naturally part of the timing system and makes sense for manufacturers to offer VVT system components that work with their current timing system components. Cloyes’ expertise in modern timing systems combined with its manufacturing and quality standards resulted in the company developing VVT actuators and solenoids that work as good as or better than OE units and will withstand abuse in the most demanding applications.

For the Ford 5.4L application, Cloyes has developed a uniquely designed actuator that is superior to the OE unit. Testing against the OE actuator, the units exhibited 20 percent less frictional drag and produced 10 percent more torque at the same oil pressure. Used OE actuators can hemorrhage oil to and from rotor chambers through worn rotor vanes that drag/seal along the stator ID. The actuators use tightly toleranced, long duration rotor vanes that do not contact the stator, therefore eliminating the wear and drag of the OE and other aftermarket designed units.

The Cloyes kits for the Ford 5.4L application include two VVT actuators with bolts, two tensioners, two chains, four guides, and the crank sprocket. Whether a guide that serves as a track for the timing chain, connecting the crankshaft and camshaft, or a tensioner, maintaining appropriate tension on the timing chain, all these components play a critical role in the timing system.

Although not included in the Cloyes kit as of now, VVT solenoids may also need to be inspected and potentially replaced. As mentioned earlier, the solenoids control the oil supply going to the actuators on each head. When a VVT solenoid is failed or failing, multiple issues could occur, such as an illuminated check engine light. A thorough inspection with proper diagnostic tools will be required to detect the reason for the check engine light to come on. Other issues related to VVT solenoid failure are rough engine idle and potential decrease in fuel economy. Again, as mentioned earlier, oil flow is directed by the solenoids into one of two oil ports that supply oil to different sides of the VVT actuator rotor vanes, one to advance camshaft timing and one to retard camshaft timing. When not properly functioning, a VVT solenoid may route oil flow incorrectly, causing a sluggish, rough engine idle. If not diagnosed, this issue could result in additional components failing as well.

Cloyes continues to develop VVT solenoids and may be offering these components in its timing chain VVT kits in the future.

Using Complete Kits and Reducing Comebacks

Timing system replacement is typically performed due to the detection of unstable operation. In that situation, and even in preventative maintenance situations, stress is experienced by all the timing system components. Chains can experience wear and stretch, guide contact surfaces can become damaged and guide bracketry can break, damage to the tensioners can occur, and sprocket tooth wear will develop when operating with an unstable chain. For these reasons, and the fact that timing component cost is a fraction of the labor costs required to replace the components, it is recommended to replace all components when making the repair. In doing so, the consumer and technician can save time as return visit may be prevented; the vehicle owner will save money in the long run as opposed to having multiple components replaced at different intervals; and the technician and shop can reduce comebacks thanks to all components being replaced at the same time.