Timing Chain/Timing Belt Repair
Timing Chain or Timing Belt?
This is one of the most common questions with a car nowadays. It is no longer a question of comparing a timing belt with a timing chain, but to understand the quality of the engines on both sides. Why is that? The short explanation is that the technology has advanced and modern engines work better with one drive system or the other. The issues can come from the engine design along with lack maintenance, not from the chain or the belt itself.
Which is better, timing chains or a timing belt?
The question of "which is better?" can never be answered. Both systems are permanently being further developed and updated. Mechanically, there is no difference between a timing chain and a timing belt. Both perform the same action and are attached to the same parts of your vehicle. The difference is in the material and location within the automobile. A timing belt is made of reinforced rubber and is housed outside the engine casing. A timing chain is made of metal links and housed within the engine unit.
While timing belts have been steadily giving way to chains due to their longer service life, belt manufacturers have made strides to improve their belt life to more than 120,000 miles, in some cases. Even though belts will not last as long as a chain, they are quieter, create less friction, and are easier to service.
In most cases, if the engine is properly maintained, service interval would be the main advantage to a chain over a belt. The chain is also, for lack of a better word, more durable. Thinking back to the days of timing belts, if the front crank seal leaked on an engine to the point of coating the belt with oil, you would most likely find the belt nearly shredded when inspecting it due to the oil saturation. On a chain-driven timing set, you simply change the crank seal, clean up the mess from the oil leak and move on.
Does my car have a timing belt or a chain?
The easiest way to know if your engine has a chain or a belt system is to take a quick look at the engine. If it has plastic covers on the front, it probably runs a timing belt because the timing belt runs dry and does not need more protection. However, if it has a sealed metal cover (to prevent the engine oil from leaking out) then it is usually a chain system.
When To Replace Your Vehicle’s Timing Belt
Unfortunately, in most cases, there are no obvious signs the timing belt is near its end of life; it can break, loose teeth or jump its timing any time. There is no visual timing belt inspection required. Timing belts have a scheduled replacement life specified by your vehicle manufacturer (check your vehicle owners manual). The recommended timing belt replacement interval is usually 60,000 to 105,000 miles depending on the vehicle and engine. In comparison, the replacement intervals for modern timing belt engines have been greatly extended (to 150,000 – 200,000 miles) due to further development and new materials.
Timing Chain Replacement
Originally, or rather back when engines were built with sturdy chains, these chains lasted forever. In today's downsized compact engines, things look different. The chains do not have a replacement interval specified by the manufacturer, but they often have to be replaced quite early because the chain has elongated (sometimes between 80,000 and 130,000 miles).
A Loose Timing Chain Can Spell Big Trouble
As a general rule, if an engine has a timing chain and the oil was changed on a regular basis, the timing chain should last the lifetime of the engine, however, service technicians are seeing timing chains fail much sooner. For an internal combustion engine to operate properly, it must exhibit exact, mechanical engine timing. More specifically, the crankshafts and camshafts must rotate in concert with one another. Timing chains are the critical link between the crankshaft and camshaft.
Tensioners make sure the chain is tightly wound to the gears. If the tensioner fails and the chain becomes loose, the timing of the engine is thrown off. And, if the timing chain becomes loose, you can get ready for serious and costly problems. If the timing chain jumps while you are driving the car, the valves could be damaged from contact with the pistons and potentially ruin the engine.
What Are the Symptoms of a Failing Timing Chain?
The very nature of a chain unit means that failure often means total calamity. If the chain breaks, the part will no longer do its job and, unfortunately, the car will no longer be able to run.
But, issues don’t always mean complete failure of the part. The chain can show signs of wear and damage before it gives way completely. Look out for the following warning signs that your timing chain is about to reach the end of its service life:
- Rattling Noise from the Engine During Start Up — A loose timing chain will rattle, usually when the vehicle is first started after sitting for an extended time. As the chain wears/stretches over use the chain tensioners take up the extra length keeping the chain tight. As the vehicle sits for an extended time the oil pressure that is pushing against the chain tensioners bleeds of releasing the tension on the chain. When you first start the vehicle the excess slack in the chain causes the chain to flop around (load and unload) as the camshaft load changes during engine rotation creating a rattling noise. This noise will usually go away once the chain tensioners are pressurized by the engine oil taking the slack out of the chain. A rattling noise of any kind coming from your engine is usually never good. At the first sign of this, get your vehicle checked.
- The Engine Is Misfiring or Trouble Starting — If the timing chain has become stretched, the calibration (timing) between the crankshaft and camshaft/s will be off. This can result in engine misfire if the valve timing is farther off than the computer can compensate for. In some cases the timing chain can skip a tooth on one of the sprockets before the tensioner has a chance to take up the slack, resulting in camshaft vs crankshaft timing error affecting combustion.
- Check Engine Light — Sometimes there won’t be any noticeable signs that the timing chain is failing, but sensors on the engine will detect a problem. In most cases there will be DTCs related to the relationship between the crankshaft and the camshaft/s. The check-engine light could mean a problem with the timing chain and should be addressed immediately.