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Tips for road testing a car

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By autotrader.co.nz

A road test can reveal a lot about a car, if you know how to recognise what's normal and what isn't. Our top 10 tips give you some important things to keep in mind when taking the ol' girl for a spin.

1: Engine noises
A well-maintained engine should tick over smoothly and relatively quietly. A loud and fast tick-tick-tick on the other hand may indicate a lifter (or on old cars, tappets) issue. A listen under the bonnet will reveal this noise comes from the upper part of the engine. A low frequency knock, from deeper in the engine, could indicate more serious bearing wear and you're best avoiding this. A shrill squeal that clears with a few revs is typically a worn/loose fan belt, confirm this by checking the tension when the engine isn't running, it’s an easy fix. Also keep an ear out for whirring noises that increase with load and rpm, these could indicate water pump, belt tensioner, alternator or A/C compressor bearings and will pay to investigate further.

2: Wheel balance
Poor wheel balance is an increasing issue as low price; low quality tyres — which can prove difficult to balance — become more prevalent. Out of balance wheels will manifest as a shake or shimmy, most often at motorway speeds so it's vital to include an open road drive in your assessment. A shimmy through the steering wheel will indicate an issue in the front wheels while a shake through the seat is usually indicative of a fault in the rear. Check for damage to the inside and outside of the rims, the odd scrape is ok, but deformation of the wheel’s shape will be forever problematic. Also run your palm across the tyres surface an d feel for high or low spots (out of round) and check for excessive wheel balance weights on the wheels, which might indicate an ongoing problem in achieving a balanced wheel.

3: Other rattles
Other causes of a shake in the front end could be a worn wheel bearing, ball joints or tie rod ends. Jacking the wheel of the ground and rocking the tyre in and out could highlight play in these components. Someone with some mechanical experience can help pinpoint the area of concern so you can make the call on if it's too big a repair to justify or something you can use to haggle on the price of the car.

4: Clicks, whines and squeals
Find a quiet car park or area to turn the steering to full lock and drive in a circle, both directions. A click-click-click-click-click noise when turning indicates a worn outer CV joint (for front wheel drive vehicles). Inner CV joints will click in straight line acceleration. A whine on overrun (when coasting with no throttle) may indicate a differential problem which can be fairly costly to rectify, it often will disappear under throttle as load is applied. Could be as simple as an adjustment or a failing pinion bearing. Will pay to have an expert confirm. Wheel bearings will also create a rumbling whir and shouldn’t be ignored. Squealing brakes may hint to low brake pad material, as they wear a steel tab is designed to rub on the disc to alert the driver of the impending service requirements. Shine a torch through the wheel to confirm all the brake pads still have plenty of life.

5: Steering
Steering should feel smooth and consistent throughout its range of motion. No notchy sensations or excessive free play in the steering wheel. If it's overly firm there may be pump problems or fluid loss. Squealing could indicate a loose belt or lack of fluid.

6: Suspension
Even if you're not looking for a sports car, suspension should be appropriately firm. Excessive pitching (nose diving) under heavier braking, unruly behavior through corners and/or failure to recover (continued bobbing motion as vehicle comes to rest) are among sure signs the shock absorbers are due for replacement. Clunking operation over bumps could be related to worn bushes, ball joints.

7: Performance
Try and test the car over as broader range of conditions as you can. If it's automatic makes sure the shifts are consistently smooth, without flaring or pregnant pauses between ratios. Faulty ignition systems are usually evident under load, if there is a hesitation under full throttle acceleration or light throttle up hills it might be related to failing spark plugs, HT leads or coils. Check engine mounts by loading engine slightly in gear at standstill with your foot on the brake (make sure nothing is in front of you) if it clunks as the engine rocks forward the mounts are probably questionable.

8: Clutch
For manual cars it's important the clutch isn't overly worn, there are three main components at risk here, the pressure plate, the clutch plate and the release bearing. A worn pressure plate means the spring tension applied to the clutch plate is diminished. It can be identified by a pedal with little resistance, little or no perceivable take up and reluctance to engage gears. A worn clutch plate will cause the clutch to slip and is the most common cause of clutch failures. A quick check is to put the car in a higher gear like fourth or fifth at slow speeds, dip the clutch pedal with a quick stab of throttle simultaneously. A good clutch will grab and the engine will shudder with the load, if the engine revs freely without engaging drive, the clutch is slipping and will require replacing sooner rather than later. Worn springs in the clutch plate can chatter when the clutch is engaged. A worn release bearing can cause grinding or whirring when the pedal is depressed.

9: Wheel alignment
Find a flat, straight piece of road and let the vehicle track without your hands on the wheel. Most alignments are designed for a slight and gradual arc to the left for safety. Anything more dramatic than a lingering, gentle arc probably indicates an alignment issue. Confirm if this has been an ongoing issue by inspecting tyre wear, poor alignment often causes uneven wear on the inside or outside edge of the tread pattern.

10: Follow your nose
With the heater vent set to fresh air, make sure there's no whiff of fuel or burning oil. A burnt oil smell may highlight an oil leak in spots you can't locate visually, as the oil makes contact with the exhaust it burns off. A fuel smell could be a fuel tank ventilation issue or a fuel leak which is obviously highly dangerous.

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