Engine Components : Engines procedures >Removing & replacing a cam belt

Removing & replacing a cam belt

Part 1. Preparation and safety

Objective

• Safely remove and replace a cam belt.

Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:

• Work clothing - such as coveralls and steel-capped footwear
• Eye protection - such as safety glasses and face masks
• Ear protection - such as earmuffs and earplugs
• Hand protection – such as rubber gloves and barrier cream
• Respiratory equipment – such as face masks and valved respirators

If you are not certain what is appropriate or required, ask your supervisor.
Safety check

• Never perform any service tasks on the engine while it is running.
• When turning the engine by hand, make sure your hands and fingers do not get caught between the timing belt and pulley.
• In order to access the timing cover and belt, it may be necessary to remove the power steering pump and/or the air conditioning compressor. Always refer to the manufacturers manual for the correct removal and refitting procedure.
• Always wear protective clothing and the appropriate safety equipment.
• Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.

Points to note

• Cam belts are primarily used on overhead camshaft engines.
• Some manufacturers have single overhead cam (OHC) double Overhead Cam (DOHC) and overhead valve (OHV) versions of the same engine. If this is the case a cam belt (although of different length) will be used on all versions of the engine.
• The number of pulleys driven by the cam belt will differ from manufacturer to manufacturer. A simple OHC fitment will have three pulleys: Crankshaft, camshaft and tensioner. Whereas a complex DOHC “vee” engine fitment will have 8 pulleys: One crankshaft, four camshafts, and three idler pulleys.

• Use the manufacturers recommended cleaning instructions. Some camshaft and crankshaft pulley damper units are dissolved by solvents.
• Always follow manufacturers recommendations regarding cam belt change intervals and replacement procedures.
• Cam belts should be kept in their packaging until required. They should be stored in an environment that has minimal humidity, consistent temperatures and is free from dust and oil contamination.
• Do not bend, twist or crimp a cam belt, as the damage will result in premature failure.
• Before fitting a new cam belt, make sure the drive pulleys are clean and free from damage and wear.
• Make sure that idler and tension pulleys turn freely and are correctly aligned.
• If a cam belt is to be reused make sure it is refitted so it turns in the same direction as before.
• Some cam belts have directional arrows and aligning marks on their outer surface to assist with fitment and engine timing.
• After fitting a new cam belt the tension pulley or adjuster should be near its minimum adjustment. If it is not, check for correct fitment.
• Always double check the various timing marks on the timing gears and timing belt for correct positioning before turning the engine over.
• Always turn the engine in its normal direction of rotation. Turning the engine in reverse may cause the spring-loaded tensioner to slacken and cause the belt to jump teeth on its pulleys.
• If an engine is undergoing repairs that require the cam belt to be removed and the belt is within 10,000 km of the manufacturers replacement interval, the belt should be changed.
• Always refit the cam belt cover once the replacement is complete otherwise the service life of the belt will be severely reduced.

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Part 2: Step-by-step instruction

1. Disconnect the battery
   Locate the battery and its negative terminal. Loosen the terminal clamp and remove the terminal from the battery post. Store the terminal so it cannot come in contact with the battery post.
2. Remove drive belts and cover
   Remove any drive belts located at the front of the engine to gain full access to the timing belt cover.
   • Turn the engine by hand to top dead center for number 1 cylinder firing.
   • Loosen and remove the front pulley attached to the crankshaft.
   • Loosen the fasteners that locate the timing belt cover and remove it.
3. Remove the timing belt
   Loosen the belt tensioner and pry it away from the belt and retighten the fastener to prevent it from springing back and placing tension on the belt. Remove the timing belt.
4. Fit timing belt
   Place the belt over the pulleys and position it correctly. Make sure that the crankshaft is still at top dead center and the camshaft aligning marks are correctly aligned. Manufacturers service manuals normally have a diagram to follow.
5. Adjust tensioner
   Slowly loosen the fastener that secures the belt tensioner and allow it to slide gently back against the cam belt. Turn the engine by hand in the direction of normal rotation for at least two complete turns to allow the tensioner to find its correct tension. Lightly tighten the fastener so it cannot move.
6. Check the timing marks
   Reposition the engine at top dead center for number one cylinder firing, and check that the location of all the timing marks are still in accordance with the manufacturers directions. Now tighten the tensioner-securing fastener to the recommended torque.
7. Refit timing cover
   Replace the timing cover and refit any fasteners. Refit the front pulley and tension to the correct torque, and replace any ancillary drive belts to drive ancillary equipment in accordance with vehicle specifications.
8. Start engine
   Start the engine and check for correct operation.