Cambelts and Timing Chains
What is Timing Belts and Chains, how do they work and Troubleshooting
In this informative article, we will look at yet another essential vehicle component that may bring about costly damages if taken for granted. Yes, we talk about the cambelt, also referred to as the timing belt. This belt is responsible for synchronizing the crank and camshaft rotation to ensure that valves open and close correctly. We will learn in due course how exactly the belt system works and talk more about the belt and chain itself. We will also dedicate time to the very important point of troubleshooting when it comes to this important component. You will realise the importance of this component at the end of our discussion; the ball will then be in your court, and whether you hit it back or not, will be entirely up to you!
Let us start our discussion by clearing the fog regarding the timing BELT and timing CHAIN issue.
What is a Timing Chain and a Timing Belt
According to AA Motoring (2016), it was common for vehicles to have a chain driven camshaft, but that changed in the 1990s when manufacturers adopted the cambelt (timing belt). The main reason for this change was to help reduce engine noise. You can think for yourself the difference in noise between a belt and a chain. So everything went well, in the noise way, but not in the wallet way! Around 2005, most manufacturers decided to bring back the chain system because consumers wanted lower maintenance costs. Manufacturers therefore spent considerable amounts of time and effort introducing improvements that eliminated many of the drawbacks of the older chain system. Let us see why they did this, and why vehicle owners preferred the reintroduction of the chain, rather than the belt system.
Timing Belts is made up of rubber and high tensile fibre, which makes them quieter than timing chain driven vehicles. The belt has teeth that fit into slots on your vehicle to hold the belt in place. If your timing belt is too loose, or too tight it can either slip or add excessive pressure, which can cause the belt to break and result in havoc. A cambelt will last you between 60 000 and 100 000 kilometre (or round about five years) before it needs replacement (depending on the cambelt’s age and the manufacturer’s specifications). Cambelt replacement is a very costly job, and the most thorough way to replace a cambelt is to replace other relevant components at the same time.
Timing chains consists of steel and lasts much longer than timing belts because they do not tend to break or wear down that easily. Improvements to the new chain system included the introduction of oil pressure and spring-loaded tensioners; these help to keep the chain stretched and quiet. Modern engines employ chain guides to silence the chain and to minimise vibrations. Maintenance on timing chains are less than timing belts because they offer a better lifespans and should last for the life of the engine (in most cases); this means that servicing costs will be less (if any). You may now make the logical deduction that chains are the chosen one above belts, but do not think for one moment that the new chain system reached its perfection! Even though chains tend not to break, they can stretch over time because they too face the worst nightmare of most vehicle components: wear and tear. This story therefore do not have a happy conclusion because if a timing chain need to be replaced, the cost of such a replacement can be significantly higher than that of a regular cambelt replacement. The good news however, is that this is a rare occurrence, so the core of the timing chain justification is that general maintenance is still less than that of a vehicle with a timing belt.
This will give you a better understanding of the difference between the cambelt and the timing time. The choice between a cambelt driven vehicle, or a timing chain driven one, will ultimately be your own personal one. Now that we know something more about the difference, we will need to have a peek at how it functions within the greater scheme of things.
How It Works
We already know that the timing belt have teeth and that it fits into slots, but that does not say much about how it works and why the belt (or chain) is so important, so let us address this. During the combustion process, the movement of the valves and the pistons need to happen in such a way that they do not collide with one another. The timing has to be perfect to prevent them from colliding with one another, and the emphasis is on TIMING. Now we should wonder why the chain and belt is called a timing belt or timing chain! We knew you would get it! The toothed timing belt (or roller chain) connects the crankshaft (for piston movement) to the camshaft (for valve movement); as such, it makes sure that each valve opens and closes at precisely the right time with relation to piston movement. In other words, it keeps your engine synchronised. In some engine designs, the timing belt/chain also drives other engine components, such as the water pumps and oil pump.
We have learned what the timing belt/chain is and how it works. Their most important purpose, as we have seen, are to ensure synchronisation. What do you think will happen when the belt malfunctions? Yes, timing will be out and this WILL cause serious damage. The most common outcome will be bent valves (the pistons colliding with the valves), but it can also damage the cylinder head or the camshaft itself. We think it is safe to say that you do not want this to happen. It is therefore important to remember that a cambelt or timing chain will deteriorate; as long as they are subjected to engine heat and varying weather conditions, cambelts can stretch, crack, and ultimately break. It is therefore important to be aware of belt or chain failure. If your vehicle lack an engine management sensor that will hopefully alert you if the camshaft and crank shaft are no longer synchronised with one another, then you should be extra attentive to any of the signs that are about to be highlighted.
If your vehicle do not want to start at all, then there may be an issue with the cambelt because the camshaft will not rotate when the crankshaft turns. A broken cambelt can be diagnosed by observing the camshaft while turning the crankshaft. No movement from the camshaft may indicate a broken timing belt. Do also entertain any other possible cause whenever your vehicle fails to start.
A worn out timing belt may have an impact on the engine’s firing rate. What may happen is that the timing belt may slip on the camshaft drive and cause one cylinder to open or close earlier than it should, and this will cause a misfire. For this to happen, most or all of the teeth on the belt will have had to deteriorate. A misfire situation may also increase black smoke coming out of your exhaust pipe.
Do not hesitate to inspect the cambelt visually. If it is worn, the belt will look glazed on the underside. This may indicate hard rubber, and hard rubber will not provide the required flexibility. Look for any cracks or unravelling of the belt. You can also press a screwdriver tip (or something similar) gently onto the belt itself, and if the applied pressure leaves no mark, then the rubber is probably too stiff. If you are unsure about the physically correct condition of the belt, then have it inspected by one of our professional mechanics. Remember the old adage – prevention is better than cure.
The cambelt is toothed, so it does not slip like a serpentine or V-belt. Sometimes, a cambelt will produce a loud noise; it can be a shrieking, grinding or rattling kind of sound. Shrieking is common for a loose belt, which can indicate wear and the need for replacement. If a new belt makes a noise, then check the tension of the belt and adjust it or have it adjusted. Do keep in mind that the noise may also come from anything else not directly related to the belt or chain itself. One example is a failing water pump pulley. If the bearings in the pulley fail, they will make a loud noise, eventually seize, and the water pump will stop to function. You do not want this to happen because your engine will overheat and that will be a costly mistake.
If you notice an oil leakage in the front of the engine, then inspect the area of the timing belt/chain. The timing belt/chain cover is secured by nuts and bolts that may loosen over time and cause a leakage. Even the gasket between the engine block and the timing cover may wear out or crack, so have this checked as well. Remember that oil ensure lubrication and heat reduction; have any leakage fixed as soon as possible to prevent damage.
In the event of you suspecting any fault with your timing belt or timing chain, and you do not possess the knowledge to address the issue, then find your way to the nearest Steves Auto Clinic. We offer friendly and professional service. As a leader in the field of automotive repairs and servicing, we are a family group that wants to make you part of the family.
Sources consulted during the writing of this article:
- AA Motoring. 2016. Engine maintenance – cambelts and chains. Online available at: https://www.aa.co.nz/cars/motoring-blog/engine-maintenance-cambelts-and-chains/ Accessed on 7 August 2018.