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lou’s garage

I drive a 2003 Jetta TDI Wagon with 125,000 kilometres on the odometer. The timing belt replacement interval is 160,000 but I had it replaced after 10 years/100,000 km. The only immediate benefit was the elimination of a "squeaky bearing" noise which would disappear once the engine warmed up. I assumed this was the water pump which is commonly replaced during a timing belt change. Was this wise or was I spending my money too soon? – Jan

The 1.9-litre ALH motor from your VW is an interference engine, which means one or more of the engine valves extends into the piston's path. The engineering of an interference engine dictates that the valves are never fully open when the piston reaches its full extension. This design leaves just enough room within the combustion chamber and contact of these components will never occur under normal operation.

If the timing belt breaks, the internal engine synchronization will be lost and a collision of engine parts will occur.

For vehicles that see less than average mileage, deciding when to perform this necessary service is a popular inquiry. It becomes an especially critical decision when dealing with an interference engine. The inconvenience of being stranded at the side of the road after a timing belt failure will be rapidly forgotten once you are handed the repair estimate to change out the belt and also repair the engine damage caused by the failed belt.

Ten years is quite bit of time on an original belt. I generally recommend no more than eight, five to seven being optimal.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing "Lou's Garage" in the subject area.

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