Does the Subaru Forester's 'boxer' engine feature a timing belt or a chain-driven set-up?

Disassemble the engine of the popular SUV, and you might find either a Subaru Forester timing belt or chain driving the valve-gear of the four-cylinder boxer. That’s because the Forester has been with us long enough to have spanned two distinct generations of Subaru engines, the first with a timing belt, the second with a timing chain set-up.

Going back all the way to 1997 when the Forester was launched here, the vehicle used Subaru’s EJ series of engines. That meant they were fitted with a rubber timing belt. That continued right through to the new model in 2008, but for the facelift of that third-gen Forester in 2011, Subaru introduced the FB series of engines, and those were fitted with a timing chain. Simply, then, a 1997 to 2011 Forester will have a timing belt, while any of the fourth-gen Foresters (from 2013 or later) will have a timing chain. And for a brief period from 2011 to 2012, the Forester was fitted with either a timing belt or a timing chain depending on which engine was fitted. The other exception is the turbo-diesel Forester which launched in 2008 and used a timing chain rather than a rubber belt.

Subaru’s factory recommendation for timing belt replacement is every 100,000km for Foresters built from 1997 to 2006, and 125,000km for post-06 models. You also need to change the tensioners at this point as these are the most common culprits for timing-belt failures. Budget on spending the thick end of $1000 for this work. The good news is that, unlike the majority of cars out there, the trade reckons you only need to replace the water pump every second timing-belt change. That’s a remarkable vote of confidence in the basic engine’s durability.

Meantime, the task of the timing chain or timing belt is exactly the same: They take drive from the engine’s crankshaft to the camshaft and, in the process, keep all the moving parts in harmony. Many car makers moved away from a timing chain to the rubber, toothed drive belt as a way of simplifying engine design and driving down the cost of each engine. The rubber timing belt is also quieter in its operation and is also less prone to stretching (as a timing chain can) so the camshaft (commonly referred to as the cam) stays in perfect synch with the rest of the engine’s rotating parts. The rubber belt is a simpler design because it doesn’t need to be tensioned via oil pressure from the engine as many timing chain systems are.

The timing chain, meanwhile, is preferred by some manufacturers because it should last the lifetime of the engine and never need replacement. This isn’t always the case, however, and some engines designs from a variety of manufacturers suffer problems in this regard. But, in a properly maintained engine of sound design, the timing chain should never need attention, while the rubber timing belt generally requires periodic replacement.