Timing belts are used to synchronize the crankshaft with the camshaft, similar to a timing chain on an overhead valve (pushrod) engine. Unlike a timing belt, a timing chain could last the life of the engine without needing service or replacement. Timing belts use raised teeth to mesh with sprockets to operate the valve train of an overhead camshaft engine.
Engines, chain or belt-driven, can be classified as either free-running or interference, depending on what would happen if the piston-to-valve timing were disrupted. A free-running engine is designed with enough clearance between the pistons and valves to allow the crankshaft to rotate (pistons still moving) while the camshaft stays in one position (several valves fully open). If this condition occurs normally, no internal engine damage will result. In an interference engine, there is not enough clearance between the pistons and valves to allow the crankshaft to turn without the camshaft being in time.
An interference engine can suffer extensive internal damage if a timing belt fails. The piston design does not allow clearance for the valve to be fully open and the piston to be at the top of its stroke. If the belt fails, the piston will collide with the valve and will bend or break the valve, damage the piston, and/or bend a connecting rod. When this type of failure occurs, the engine will need to be replaced or disassembled for further internal inspection; either choice costing many times that of replacing the timing belt.
Whenever a vehicle with an unknown service history comes into your repair facility or is recently purchased, here are some points that should be asked to help prevent costly engine damage:
All models covered herein, except the1993-97 Passat with the VR6 6-cylinder engine, use a toothed belt to drive the camshaft(s). This design is lightweight, and offers a low amount of parasitic drag on the crankshaft, which increases the output of the engine. Additionally, inspection and replacement of the belt is a relatively simple task (as opposed to replacing a timing chain and sprockets) ensuring that the engine is operating at its peak efficiency. On some models special tools may be required
The timing belt is a basic, yet critical engine component. If the belt were to break, the valve train can be seriously damaged. Frequent inspection, adjustment, and replacement of the timing belt and tensioning pulley is a must.
Audi and Volkswagen Do NOT list a replacement interval for timing belts for their later engines. Because of the consequences of a snapped timing belt (likely to result in significant engine damage), check the timing belt at regular intervals, and keep a record of the mileages checked.
On the 1990-93 2.0L 16-valve Passat GL/CL models, the timing belt should be checked every 2 years and replaced as necessary, or replaced every four years or (60,000 miles (96,000 km), whichever occurs first.
On all 1995-96 Passat GLS models, the timing belt and rollers should be inspected and adjusted as necessary at least every four years or every 60,000 miles (96,000 km) and replaced as necessary, especially on vehicles subjected to severe use. On all other models, if not replaced previously, replace the timing belt and rollers at 90,000 miles or every 6 years, whichever occurs first.
During inspection, check the belt for fluid contamination, cracking, damaged teeth and separation. If the belt is suspect in any of these areas replace the timing belt.
Inspect both sides of the timing belt. Replace the belt with a new one if any of the following conditions exist:
If none of these conditions exist, the belt does not need replacement unless it is at the recommended interval. The belt MUST be replaced at the recommended interval.
Removal & Installation
1.8L (AEB) Engine
- Note the radio security code and disconnect the negative battery cable.
- Place the (hood) lock carrier in the service position. For additional information, please refer to the following topic(s): Body And Trim, Service Position, Front Bumper, Hood Lock Carrier.
- Remove the engine accessory drive belts. For additional information, please refer to the following topic(s): General Information And Maintenance, Routing Maintenance And Tune-up.
- Using a 5 x 60mm bolt, secure the viscous fan pulley. Using a hex wrench, remove the viscous fan-to-pulley bolts. Remove the viscous fan assembly.
- Turn the engine by hand to Top Dead Center (TDC) on the firing stroke for cylinder No. 1.
- Remove the upper timing belt cover.
- Using the center bolt, rotate the crankshaft in the direction of engine rotation to position the No. 1 cylinder at Top Dead Center (TDC) of its compression stroke.
- Remove the damper pulley-to-crankshaft bolts and the damper.
- Remove the lower timing belt cover.
- Using a Torx® Wrench T45, or equivalent, loosen the timing belt tensioner, push the tensioner downward and remove the timing belt.