how much is my car worth for scrap

Cam Belt Failure – What It Is & How It Happens

Collision damage from crashes aside, one of the most common reasons people use our service is down to engine damage caused by failure of the cambelt or timing chain. It usually means that a car requires a new engine, or at least a top-end engine rebuild and in most cases the cost to do that is more than the value of the car itself which is why many choose to sell it for scrap or salvage.

Why are Cambelts/Timing Chains So Important?

The engines in most cars are four stroke engines. As the pistons go up and down they suck in air and fuel and compress that mixture which ignites, causing an explosion to shove the piston back down. On it’s way back up again it forces the burnt mixture out again – which, in short, means: Suck, Squeeze, Bang, Blow which you can see in action in the animation below. Although in real-life it operates much, much faster!

4StrokeEngine_Ortho_3D_Small
Image credit: Zephyris, CC BY-SA 3.0, Link

With so many parts of metal moving at such speeds, it’s vital that the valves at the top of the engine don’t come into contact with the pistons – which is why timing is crucial. The belt with the arrow on the left hand side of the above animation represents the cambelt, or timing chain. Its job is to make sure that when the piston is heading rapidly upwards the valves remain closed or are only open just enough that the piston doesn’t touch them and so when a cambelt or timing chain fails, this finely tuned system gets out of sync, or out of line which means that the moving parts within your engine are free to collide, causing catastrophic and usually terminal damage.

What Can I Do To Make Sure This Doesn’t Happen?

Regular scheduled maintenance. When manufacturers design and test engines they attribute a lifespan to different components with a decent safety margin built in. If you look in the service handbook of your car it will tell you when the timing chain or cambelt should be renewed. This is generally related to mileage, but also time. Timing chains are made from metal but cambelts are typically made using rubber and so it perishes with both time, and use, which means that even if your car doesn’t do many miles the cam belt will eventually wear out.

Are Cambelts Expensive To Replace, And Why Do Garages Keep Quoting For Changing The Water Pump Too?

The timing belt or chain on your engine doesn’t only control the opening and closing of the valves but they also drive the pump which moves water around the engine to prevent it from overheating. Like the belt, the pump has a limited life and since neither component is particularly expensive to replace, it is often best practice to change both at the same time to save on labour costs. Plus, the few hundred pounds to do this job now, is far better value than a few thousand for a new engine or car!

How Do I Know If The Cam Belt or Timing Chain Needs Replacing?

Research
The internet is often your best friend. If you have a car in mind then type its make and model into Google followed by the words “known issues”. This will quickly supply you with a list of things to look out for when you start shopping or, possibly, reasons you should choose a different model…

Be Sensible
Don’t fall into the “it won’t happen to me” trap. If an issue has happened to enough other people then the chances are high that it will happen to you

History Is Important
If the car you are looking at doesn’t have a stamped service book or history then walk away. Cars are made in their thousands so even if you have a particular model, specification and colour in mind you can afford to be choosy. Take your time and find one that has a decent pedigree.

Drive a Hard Bargain
If you are buying from a dealer and you can’t see in the service history that the cambelt has been changed recently then make that a condition of your purchase. If you’re buying privately then be prepared to haggle hard and use the money you manage to save from haggling, to get the job done yourself at the earliest opportunity.

What Do I Do If A Cambelt Or Timing Chain Fails Prematurely?

There isn’t much you can do to prevent this, minus changing them regularly, but that’s an incredibly uneconomic way to solve a problem which may not even occur. However, there are steps you can take to avoid being out of pocket. It’s tempting in this kind of situation to go to an independent garage for a cheaper fix, but that’s not always the case. Even if your car is out of warranty, if it is still relatively new and you are confident that it has been serviced and maintained as scheduled make sure you return the vehicle to a main dealer as manufacturers don’t like bad publicity and it could be something which the manufacturer will authorise the dealership to fix at their expense. This is usually the case if it is an obvious issue or you can demonstrate that it’s premature component failure. Plus there’s always the chance that if they won’t cover the full cost of the repair, they may offer a financial contribution as a gesture of goodwill in effort to retain you as a customer. Of course if you are reading this after the fact, then all of the above will be little consolation but it will hopefully go a long way towards ensuring that lightning doesn’t strike twice.

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