Car Buyers' Guide: Reducing the risk when buying used

By Jack Biddle

Engines respond to a bit of respect

Choosing a car with a good service history can save you a lot of money in the long run. Photos / Getty Images
Choosing a car with a good service history can save you a lot of money in the long run. Photos / Getty Images

Sam is looking for a vehicle with a reduced risk of major mechanical failure or high maintenance costs.

He is also aware of the reliability record of the Japanese brands in his price range but does not want to dismiss other options. The Budget: Around $12k-$15k

The oil in every case had basically turned to sludge causing the oil pump strainer to block and therefore, create a lack of pressure and flow to the main moving internal parts of the engine. End result was either a total engine rebuild or a second hand engine being fitted to help reduce repair costs.

So while we can bring to your attention a number of different alerts and potential high risks to avoid, don't forget even the simplest of mechanical componentry can fail prematurely due to a lack of regular checks and servicing.

• Read more Drivers take selfies behind wheel
• Read more Relicensing tips you need to know

Finding a vehicle with a proven regular servicing history can turn a potential high risk into a make/model worth owning.

The recommendations made below, are also based around the assumption that some sort of pre purchase inspection is carried out prior to committing to purchase any vehicle. And we will stick with petrol powered vehicles.

Belt v chain-driven engines (the vital link between crankshaft and camshaft)
Rubber cambelts need more servicing than chain drives.
Many will say a vehicle fitted with a chain driven engine is bullet proof because there is no manufacturers recommended replacement time/distance like a rubber belt which, if not replaced, can break without warning causing extensive engine damage.

While there is some truth in those comments, it should also be remembered that chains can and do have their own issues at times mainly due to stretching (often caused by lack of servicing and contaminated engine oil). Because a chain is installed deep within the internals of the engine, labour and parts costs can be extremely high to replace.

The rubber cambelt however is fitted outside of the main engine assembly which makes replacement a far less intrusive and time consuming task.

Once a cambelt is replaced, it's normally good for five years or 100,00km (whichever comes first) before owners need worry.


V-shaped or in-line engine (the way the engine design is configured)
For simplicity, let's compare a V6 engine with an in-line 4-cylinder power unit of similar power output.

While the V6 is a very smooth engine it is also more complex than the in-line 4-cylinder power unit. For example with a V6, there are two cylinder heads (V6 has two banks of 3-cylinders mounted on the main engine block) as opposed to a single cylinder head only with an in-line engine.

So there is a lot more labour and parts required if major rework is undertaken in this area. Plus it's not uncommon to have to disconnect engine mounts and manifolds to replace spark plugs or check coil packs on front-wheel-drive vehicles fitted with V6 engines pushing regular maintenance costs higher at times.

Turbocharged v non-turbocharged engines (turbocharging pumps additional air into combustion chambers)
Turbocharging an engine has become a lot more common these days in the strive to reduce tail pipe emissions and fuel consumption.

In your price bracket however the emphasis would be more on using this technology to increase power. As turbocharge engines age they can require compared with a non-turbocharged engine would cost. Their longevity can also be enhanced by using the recommended oil grade and not tampering with or modifying the air induction system.

Transmissions
Repairing automatic transmissions can be costly.
Some automatics are a lot more expensive to repair than others but you still don't get much change out of around $1400 these days for even the easiest and most common transmission overhaul. Manuals in the main have a greater life expectancy provided a vehicle has not had a hard past life. Clutch performance can usually be gauged with a simple slip test during road test.

General
Most garages will tell you that if there was one mechanical failure you need to try and avoid it is overheating an engine.

Severe melt downs can happen very quickly and can end up with an engine that is only good for scrap. Some European brands are renowned for cooling system issues and weaknesses, mainly due to the use of plastic type materials in components like thermostat housings and over time they can become very brittle and start to leak under pressure.

The more mainstream brands can also suffer from cooling system issues however due to seepage from the radiator top and bottom tanks which are also manufactured from a plastic compound. Bottom line when getting any vehicle checked out; pay particular attention to signs of coolant loss, recent repairs and any evidence of a past overheating issue.

Follow Driven on Facebook and Twitter for the latest motoring news.

- NZ Herald

© Copyright 2014, APN New Zealand Limited

Assembled by: (static) on red akl_n1 at 24 Sep 2014 11:14:17 Processing Time: 720ms