The tension arm has an aluminum base with a nylon surface. According to Ford Technical Service Bulletin 03-15-7, excessive wear in the timing chain tensioner arms can cause a noisy condition. The chain damper, tensioner, guide or rails should also be replaced when the chain and sprockets are replaced because these components play a vital role in supporting the chain and keeping it tight.Ī case in point is grinding noise coming from the timing chain cover area in 2000 to 2003 Ford Crown Victoria and Mercury Grand Marquis with the 4.6L V8. On OHC engines that use a timing chain, the timing set may also include a chain damper or tensioner. These parts are included in a typical three-piece timing set.
The camshaft and crankshaft sprockets should also be replaced along with chain. A high mileage timing chain that has stretched and is loose can’t maintain accurate valve timing and should be replaced if play exceeds specifications. Don’t take a chance reusing an old timing belt, chain or gear set.
If an engine is being rebuilt, the timing belt, chain or cam gears should always be replaced. On newer engines, the original equipment belts are made of better materials and usually have a service life of 100,000 miles or more. For older (typically mid-1990s and back) engines, the recommended replacement interval for timing belts is usually 60,000 miles. The best time for a vehicle owner to replace a timing belt or chain is before it fails.
The engine may continue to run but will experience a loss of performance because of the altered valve timing. Timing chains or belts may also jump time if loose. Interference engines include most Acura, Honda, Hyundai, Infiniti, Isuzu, Nissan and Porsche engines, also some Audi, BMW, Mazda, Mitsubishi and VW engines, as well as Chevrolet 1.5L and 3.4L, 1995 and newer Chrysler 2.0L and 2.5L, 1997 and newer Chrysler 3.2L and 3.5L, and Ford Probe 2.0L and 2.2L engines. A cam drive failure can also cause expensive valve damage in "interference" engines that don’t have enough clearance to prevent the valves from hitting the pistons if the cam stops turning or jumps out of time. If a timing belt or chain breaks, or the cam drive gears fail, the cam stops turning, the engine loses all compression and the engine stops running. The increase in length can have an adverse effect on camshaft timing and become a source of noise if the chain becomes loose enough to rub against the inside of the timing cover. Timing chains, by comparison, are mostly immune to the effects of heat. The cords inside the belt also weaken as the belt accumulates wear, increasing the risk of the belt breaking. Over time, this causes the rubber to lose flexibility, harden and crack. As a belt wraps around and turns the sprockets, friction creates heat (this is in addition to the heat from the engine itself). That’s why belts are used on many OHC engines. But chains are also heavier, noisier and more costly to replace. Chains are more durable than belts and typically have a longer service life. Chains are made of steel links connected by flexible rollers. Belts are made of synthetic rubber reinforced with tough fiber cords that provide tensile strength and prevent the belt from stretching. They have to turn the cam with enough force to overcome the resistance of all the valve springs. Timing belts and chains carry a heavy load.
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