Cam Phaser Replacement

22-08 Follow replacement procedures for components on a VVT engine.

Performing replacement of a cam phaser is a task that may be required to solve a variety of VVT issues. Replacement may be necessary due to an actuator/phaser that is leaking or binding or due to damaged or worn gear drive teeth from contamination or normal wear. When servicing a VVT phaser, the assembly will need to be replaced. Individual replacement parts are not available from OEM or aftermarket sources. While it is possible to disassemble and clean varnish from the actuator, if not all of it is removed or if the actuator is damaged while cleaning, the actuator may need to be repaired again. Therefore, actuator replacement is recommended whenever an issue is present (FIGURE 22-40).

FIGURE 22-40 The phaser should be replaced as a unit to ensure all the internal components will operate correctly.

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When replacing a VVT phaser due to oil sludging and poor maintenance, service procedures may recommend flushing the crankcase to remove the contaminants. Follow the flushing procedure by changing the oil and filter. Provide documentation to the customer before flushing, stating that the engine is badly sludged, but this flushing may or may not be beneficial. In the cases of severe sludging, flushing can cause a blockage in the oil pickup screen or oil galleys. Debris and contaminants that break free during flushing are suspended in the oil, traveling throughout the entire oil system. Severe sludging typically requires engine replacement, or a thorough overall involving deeply cleaning the block and cylinder heads is required.

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Before servicing any VVT system, always refer to the manufacturer’s technical service bulletins (TSBs). The concern at hand may have a related TSB that can save time and prevent repeat repairs.

Note: Checking TSBs for most vehicle problems is part of a well-planned diagnostic path. The time spent performing a quick search for related information can save valuable time later. Improvements and updates regarding diagnosis, PCM updates by reflashing, and updated parts and procedures are contained in TSBs.

Replacement procedures vary considerably, from a relatively simple process to a significant repair. Removing the cam phaser can be challenging due to limited access and the location of other engine components that would need to be removed to access the valve cover and/or timing covers.

When installing the phaser, the camshaft and crankshaft will need to be rotated to a specific position before installing the new phaser. Also, ensure that the new phaser is in its proper position. Locking the phaser in a basic setting position may be required before installing it. Verify and follow the proper repair procedure provided in the vehicle’s service information. Replacing the phaser may require also replacing the attaching hardware, bolts, washers, and shims. Follow proper manufacturer reassembly procedures, and ensure that the bolts are torqued to specification.

Timing Chain Replacement

Timing chains typically have a long service life, but occasionally, they wear and stretch (elongate at the link holes) while in use and may require replacement. When replacing a timing chain due to wear, the components that it contacts and that apply tension to the chain also require inspection for wear (FIGURE 22-41).

FIGURE 22-41 A timing chain has a much longer life than a timing belt, but it is still susceptible to wear and stretch. When it is determined that the timing chain needs replaced, all the components must be inspected to determine their serviceability. Most timing chain kits come with all the wear components for replacement.

Timing Chain–Related Component Inspection and Replacement

If any part is suspect or questionable, replace it. When servicing any cam timing component, use the proper tools and service information. Failure to adhere to either of these recommendations can result in engine damage.

• Sprockets and gears: Inspect for sharp pointed teeth, indicating wear.

  •  If discolored, it could represent a lack of lubrication, causing the component to overheat.

• Tensioner: Check the tensioner for signs of collapsing; if it’s hydraulic, check for leaks.

  •  Also, check for signs of binding, sticking, or wear.

• Chain guide/rails: Check for visible physical damage.

  •  Guides and rails can wear through.

• Hardware: Replace one-time-use hardware when servicing.

  •  If the hardware shows signs of damage or is missing, replacement is required.

  •  Refer to service information for one-time-use components, typically noted prominently in the service literature.

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When rotating an engine over for timing chain or belt replacement, verify that the engine rotation is in the correct direction. Some engines do not use a keyway to locate the cam and crank gears. Turning the engine or camshaft over in a counterclockwise rotation can loosen the bolt, allowing the gear to move independently of the camshaft, altering the camshaft timing. If this happens, the engine’s base timing will need to be reset to prevent engine damage and poor engine performance.

Timing Belt Replacement

Unlike timing chain replacement, for an engine that is equipped with a timing belt, the manufacturer typically recommends a maintenance procedure at specific mileage intervals. As with timing chain service, always follow proper procedures from the service information. An improperly timed engine can result in engine damage or poor performance.

Before replacing the timing belt, check for TSBs that may contain updated parts and procedures. Manufacturers continually change procedures and update parts during the vehicle’s build, known as running changes (FIGURE 22-42). Therefore, the part(s) being installed may appear different from the part removed, as well as modifications to the service procedure to incorporate these parts and/or procedures.

FIGURE 22-42 Just like installing a timing chain, following the procedure to reset the phaser to time the engine must be followed precisely; otherwise an out-of-time condition may occur. With an interference engine, improper operation may cause an intake or exhaust valve to come into contact with the pistons.

Reasons for Timing Belt Failures

• Improper tension is typically a result of overtightening a belt removed for another service.
• Belt contamination can stem from a variety of sources, including oil, coolant, or other engine fluids that are leaking or have been spilled.

  •  Do not reuse a belt contaminated by oil or coolant.

• Failed water pumps need to be carefully inspected for physical damage to the water pump teeth and for coolant leaks.

  •  If the water pump teeth have been damaged, it typically results in belt damage as well.

  •  Closely inspect the belt for tooth damage and edge wear.

  •  Do not reuse any belt that exhibits signs of wear or damage.

• Belt damage caused by loose or damaged covers allowing debris to contact or run in the path of the belt, causing damage.

  •  All covers and seals must be present to prevent damage to the belt.

• Snow, ice, or mud may pack inside the belt cover, which can cause the timing belt to jump.

  •  Snow or mud entry can occur from missing or improperly installed covers, missing or incorrectly tightened bolts, or an engine used in severe off-road use.

  •  Always verify that installation of timing covers includes that all seals are in place and that the cover is secured correctly.

  •  Check TSBs for possible updates to covers and seals if the manufacturer finds that the covers are experiencing a concern.

  •  Timing belt damage requires replacing it; do not reuse it.

  •  Check service information for one-time-use hardware and replace as directed.

• Belt damage can happen during improper assembly, allowing piston-to-valve contact.

  •  Belt damage can occur for various reasons, including multiple markings on a gear that may be confusing if service information isn’t followed.

  •  Damage caused by contact will require timing belt replacement and inspection of internal engine components.

  •  Damaged engine components will require replacement.

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Some manufacturers incorporate the water pump either into the timing belt routing or behind the covers that shield the belt. When servicing the timing belt on any of these engines, replace the water pump during timing belt service. After removing the timing belt, perform a thorough visual inspection for oil leaks at cam and crank seals and engine sealing mating surfaces.

Variable Valve Timing Diagnosis

VVT faults can produce a noise-related concern or a drivability concern. Drivability faults typically result in a DTC, whereas noise concerns may or may not set a trouble code. The oil condition and level have a major impact on the camshaft actuator system. Low oil levels, or sludge and debris contaminated oil, can also set a DTC and cause incorrect system operation.

Noise Diagnosis

Timing chain(s) and hydraulic phasers can both result in excessive engine noise after start-up. Timing chain stretch and tensioner or rubbing block failure all contribute to engine noise that may be worse after a cold start. A failed VVT actuator pin can also cause the same type of noise during a cold start. To determine which is at fault, remove the valve cover(s). Turn the engine over manually in each direction (be careful not to loosen the crankshaft bolt on some manufacturers’ engines, due to the lack of a keyway on the crankshaft). If the camshaft does not move with the cam gear, it indicates that the locking pin has failed. If timing chain slack that moves from side to side when rotating the engine is noticeable, the tensioner ratchet has failed and will require replacement. Hydraulic timing chain tensioners can leak oil pressure, causing undue stress on the ratchet mechanism that over time will cause it to fail. As always, verify what caused the concern; repair the cause, not just the result.

Timing-related noises may be a result of a tensioner bleeding off oil pressure during an extended soak time. Reduced timing chain tension results in a rattle or slapping noise present on cold start-up. To isolate the cause, listen for the noise after both cold and hot starts. If the noise is only present during cold start-up, suspect a tensioner concern. To verify this, check timing chain tension hot and cold because a failed lifter or follower can also cause an identical noise on cold start.

Timing component damage is typically a result of low oil pressure. Broken chain rails can occur from timing chain slap caused by low oil pressure failing to keep the tensioner extended correctly. Tensioners can also fail from a lack of oil pressure. Noises present only at hot idle are almost a guarantee of a low-oil-pressure issue. To quickly verify low oil pressure, check the cam timing error or difference PIDs during cold and hot idle and at higher rpm. If the timing is erratic only during hot idle, then subsequently check oil pressure when it’s hot.

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A failed ratchet mechanism in the tensioner that goes unchecked for an extended period is typically the cause of a jumped timing chain(s). Jumped timing chains can also occur if the technician turns the crankshaft opposite to its normal rotation; a weak ratcheting tensioner may also allow the timing chain to jump. If the engine ran well when pulled into the service bay but runs poorly after repairing the engine, suspect a jumped chain. In addition to noise during start-up, a pin that fails to lock can cause intermittent stalling, hesitation, rough idle, and low engine vacuum.

During engine disassembly, perform a quick check of the location of the timing chain tensioner before removing any timing component. If the tensioner is less than halfway extended, it indicates that the chain has not stretched and that the tensioner and guides are mechanically OK. If timing components are serviced when they’re disassembled, however, replace the chain(s) and tensioners on vehicles that have accumulated significant mileage.

Noise issues can also be the result a lack of oil pressure to the timing chain tensioner from a clogged pickup screen or blockage of the tensioner oil pressure channels in the block—resulting from sludge or hard buildup of carbon deposits. A combination of low-tension piston rings and PCV systems, particularly on gasoline direct-injection (GDI) and variable cylinder engines, are particularly susceptible to developing these issues, with some manufacturers experiencing far greater issues than others. If oil pressure is restricted, it can cause a slapping noise on start-up or a jumped timing chain. To check for a restricted oil pickup, drain the oil and insert a borescope into the oil drain hole to inspect the pickup screen. The hard carbon deposits may float away during oil draining, so if they’re suspected of being an issue, drain the oil through a paint filter to capture and collect the deposits.

As with all diagnostic procedures, begin diagnosis with the least intrusive tests. Before performing non-intrusive testing, always perform a visual and audible inspection first.

The following lists the least intrusive tests:

• Check oil level, pressure, and condition: A larger number of VVT concerns result from low oil level or incorrect pressure or viscosity. The majority of oil system faults are a result of a lack of maintenance.
• Retrieve DTCs: This is one of the first steps to perform when diagnosing engine performance concerns regardless of the system at fault.
• Check vacuum: If codes set for CMP or performance, perform a quick vacuum test. If the vacuum is normal at idle, either it is a VVT control fault or a component is sticking at rest (no camshaft timing adjustment). If the vacuum is a few inHg (kPa) low, a mechanical fault is present in the engine. A jumped/stretched timing chain, a stuck VVT actuator that is not at rest, or a spool valve sticking allows the camshaft timing to be altered when it should be at base at idle.
• Monitor PIDs: Some research may be required to understand how the manufacturer explains and displays its PIDs. While the hardware is relatively consistent in a VVT system, software and terminology can and does vary widely by manufacturers. For example, degrees displayed may be camshaft or crankshaft again; research is required to aid in proper diagnosis.
• Activate the system: Using output controls or fused jumper leads, dynamically test the system while monitoring PID data. This test is typically quick and easy, stressing the entire VVT system.
• Complete a power balance test: If only one cylinder shows a fault of lower cylinder output, it is not a fault of the cam timing. If an entire bank has low output, this could be a result of incorrect cam timing.
• Complete a relative compression test: Use a scan tool or a scope and a high-current clamp to monitor the starter draw by cylinder.
• Use an oscilloscope to monitor camshaft and crankshaft relationships: The cam-to-crank relationship helps to determine whether a fault is present, preventing unnecessary and time-consuming engine disassembly to search for a fault.
• Perform a manual compression test: If the relative compression test shows signs of a concern, perform a manual compression test to help diagnose valve or piston concerns or to isolate the concern to a cylinder, block, head, or gasket.

  •  If the manual compression test shows a compression pressure higher than specifications, two concerns are possible:

  1. Cam timing is advanced, due to either jumped cam timing or a VVT malfunction.
  2. A decrease in combustion chamber size, typically due to carbon buildup on the top of the piston or in the combustion chamber.

  •  If the pressure is lower than specifications, it is an indication of improper valve train operation, leaking valves, or a hole in a piston.

• Perform a cylinder leakage test: Check valve timing if all cylinders have low compression that is not the result of cylinder leakage. If only one or two cylinders have low compression, perform a cylinder leakage test. Performing this test locates leakage due to valve(s) or ring-sealing faults. Depending on the location of the leak, this test could indicate intake or exhaust valve concerns, a piston ring or cylinder concern, a cracked head or block, or a head gasket concern. If all cylinders are low on compression suspect a mechanical problem.

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If compression is above specification, check for advanced cam timing, a result of a VVT malfunction or jumped timing from a mechanical failure or improper assembly.

Variable Valve Timing Testing Goals

Use the following steps to diagnose VVT systems:

1. Determine whether the base or default cam timing (position) is correct:
   • Use of scan tool.
   • Use the scan tool graph or scope, check the crank and cam signals to compare their relationship (synchronization).
   • Use a pressure transducer connected to a lab scope to test in-cylinder pressure (advanced level diagnostics).
2. Determine whether the cam phaser moves throughout its entire range (phase angle).