Entries from February 2007 ↓

Preamble
Last week we read about odours in a car. Since it’s a piece of complex machinery in motion, some noises are inevitable even though today’s cars are a lot quieter than their decade old siblings. Some of these are normal where as some are like coming events…

Unfortunately, an average owner-driver is unable to distinguish between the two. So let’s try and explore these.

1. Normal Noises
To qualify these, let’s take the noises a new car makes when you first drive it as ‘normal’ - assuming it didn’t have any defects. These can be broadly subdivided as relating to - i) Engine/Transmission, ii) Suspension, iii) Under chassis and iv) Body/doors/panels.

First types will be lowest when the car is stationary with engine idling. Such ones will progressively go up depending upon - a) engine rpm and b) road speed. In the former category, ‘refinement’ of the engine/transmission design and ‘build-quality’ holds the key whereas in latter, ‘rolling noises’ depending on tyre/tread pattern vis-a-vis road surface AND the front/rear Suspension Design gain prominence.

2. Abnormal Noises
Keeping in mind that ‘all aluminium’ engines are noisier than cast iron block types, it’s interesting to note that all the refinement of engine/transmission design can go for a six if the rolling noises predominate at higher speeds, in some makes from as low as 20 kph upwards. To a large extent, narrow footprint tyres preferred by OEMs due to better fuel efficiency are mainly responsible for such rolling noises, closely followed by faulty suspension design that leads to ’structural resonances’.

On the engine/transmission related noises, even in a healthy engine excessive ‘valve/tappet clearances’ can add significantly to the noises it’d make. In addition, faulty foundations of engine/gearbox too can add to them. Besides, ‘peripherals’ like drive belts, water pump, AC comp., power-steering pump and alternator bearings too can get noisy, with impending failure. It should be kept in mind that any engine/gearbox/accessories will get noisier as they get older/wear out.

Over and above, the most common noises in Front Wheel Drive Cars are from wornout ‘axles’. Every FWD car has two of them and each has two very hi-tech ‘Constant Velocity Joints’ at its either end, covered with Synthetic Rubber Boots and packed with special ‘Moly’ grease within. Normal life of such CVJ’s in our conditions is ~ 60,000 kms PROVIDED their SRB’s don’t suffer any premature failures as is quite common on our grit-laden roads, especially during the rainy season. Once that happens, the special grease escapes from the CVJ/SRB’s and dirt gets in - leading to the CVJ getting damaged in no time.

The rattling noises a wornout CVJ makes are quite characteristic and as a thumb rule, the lhs ones are the first to give way for understandable reasons. If an Axle rattles while turning, even on take off from standstill, it’s the ‘wheel-end’ CVJ that’s gone. On the otherhand, if such rattles are heard on accln. or de-accln., then it’s the ‘drive-end’ CVJ that’s wornout.

In such situations, it’s wise to replace the entire Axle assy with an OE part for lasting relief, though expensive, as regardless of what one may advise it’s next to impossible to satisfactorily re-furbish such hi-tech CVJ’s in the after market.

3. Suspension Noises
These can be broadly classified as - i) Soft ‘thuds’ and ii) Rattles. When the soft thuds become louder and occur without much provocation, as going over small potholes, one’s Shock Absorbers will need looking into. If there are ’squeaks’ emanating from under-sides, it’d be various Suspension Rubber Bushes that’d need attention. Normal life expectancy of such parts on our kind of roads is ~ 50,000 kms and that too if the car is driven carefully.

Rattles, on the other hand, signify some things loose or mis-aligned with car’s under-sides. Most common culprit is the exhaust line that’s either damaged due to a hit or unsatisfactory repairs done while replacing a muffler etc.

4. Steering Noises
While some ’soft ones’ are inevitable especially on our kind of roads due to the inherent ‘multi-link’ nature of such mechanisms, when they get louder and manifest without much provocation that one needs to attend to them.

Such noises can arise either from loose or wornout - i) ‘ball-joints’, ii) ‘rack and pinion’ assy incl its 2xguide bushes, iii) unbalanced front wheels and iv) steering column bearings/bushes and/or its ‘universal joints’.

Logically, these should wear out time/distance wise in the same sequence as above but lapses in their manufacturing quality or assembly can create exceptions. Above all, fair amount of skill is needed in identifying the real culprits coz every thing out there is so ‘inter-connected’.

5. Doors and Windows
Such noises are perhaps easiest to locate for a layperson and can afflict even a new car. From doors, they’re due to their mis-alignment with the body frame or excessive slack in their locks/latches. Ill-secured door panels too can vibrate and make noises. On other hand, window glasses tends to ‘chatter’ if not fully raised or lowered - unless their guide ‘channels’ are wornout due to age - usually beyond 3-years.

Also read:
How do I keep my car trouble-free
Smells in a car

Preamble
Now that we have had a look at how to keep our cars trouble free. Well, here’s some more - keeping in mind that cars are somewhat like other living beings and let off distress signals when all is not well with them. So as an intelligent owner/driver, it’s worthwhile to detect them in good time before it’s too late - be it as a driver or as a passenger.

1. Fuel Odours:
Such smells can be most dangerous of them all - implying a potential fire hazard. These arise due to either a perceptible leak or ’sweating’ in the ‘plumbing’ between the fuel tank and the engine. A competent Garage or a DIY owner can spot them by inspecting the fuel lines to and from engine to fuel tank and take remedial measures.

However, in some of the present day cars, in-cabin fuel odours are often noticed even when the above plumbing shows no flaws. These have been traced to a faulty gasket on the fuel tank flange for accessing the fuel pump/level gauge under the rear seat! In the older non-Mpfi cars, in addition, these could also arise due to ‘over-filling’ the fuel tank.

2. Burning Odours:
Present day cars deploy a variety of synthetics and plastics within and outside their cabins. A ‘normal’ person can distinguish amongst these as those arising out of - a) Friction materials used on Brake Linings/Clutch Plates, b) Rubber or Plastic Parts and c) Lube Oils or other engine fluids.

The friction material odours can arise due to ’sticky’ brakes or more commonly, the Parking Brake not having been released fully. A Clutch too can give out burning smells if ‘rode on’ in heavy (b2b) traffic or uphill.

For rubber type odours, under inflated tyres are the most common culprits and plastic types prima-facie mean overheated electrical wiring either within or outside the cabin. Most common cause for such ones is the deployment of ‘unauthorised’ and crudely installed electrical accessories such as a high-powered Music System or a Remote/Central Locking System.

In addition, if the roof lamp is left on for long times, its plastic cover can over heat and emit such odours. Tampering with OE wiring harness is an absolute taboo with the present Mpfi Cars.

On the other hand, Oil/other fluids’ burning type odours invariably imply either an overheated engine or oil leaks from the engine/gear box coming into contact with exhaust line that can run as hot as 500.C+ next to the engine - tapering off to nearly 100.C towards the tail end. This too can be a fire hazard. Brake Fluid leaks within the wheel assemblies can also emit burning smells, as brake discs/drums can get very hot under hard braking.

3. In-cabin Odours:
The last of in-cabin odours can be ‘organic’ type - let off by decaying matter within. Most common ones are from the Car AC, due to rotting matter deposited on its Cooling Coil. Since such matter can gain access via the fresh air duct if kept open and in our conditions, it’s advisable to keep it shut most times. The only remedy here is to have the AC/Cooling Coil Serviced, which can be a time consuming and expensive. As in most cases, prevention is better than cure.

Other major offenders in this class are debris of eatables accumulating in the inaccessible corners. The best thing to do is to avoid any eatables inside the car especially with children and if inevitable, have the car internals first vacuumed thoroughly and only then have the various nooks and corners blasted out with compressed air - only to be vacuumed again. If ‘pre-vacuum’ were omitted, most of the dust so dislodged would settle down on the AC Cooling Coil - with its own undesirable consequences.

Having ensured all these, it’s a good idea to keep a car ‘air freshener’ inside but mind you, let it not be like spraying perfume to suppress bad body odours!

Also read:
How do I keep my car trouble-free
Noises in a car

Preamble
Besides noises, in any car some ‘vibrations’ are inevitable. These are ‘noises’ that can be ‘felt’ but not heard. It can be difficult for an average person to distinguish between normal or abnormal vibrations. So let’s try and explore them…

Causes of Vibrations
It’s elementary physics that any rotating mass will vibrate if its weight is not evenly distributed around its ‘axis of rotation’. Their ‘intensity’ is proportional to such ‘unbalance’ AND speed of rotation. If vibrations are not contained to ‘safe’ levels, ‘metal-fatigue’ sets in a machine, eventually leading to its wreckage.

Prime source of vibrations in a car is its engine – followed by wheels and road undulations transmitted to its body by its suspension. Let’s look at each of them.

Engine
The ‘reciprocating’ movement of pistons in an engine is converted to a ‘rotary’ one by its ‘Crankshaft’, which is linked to them by ‘Connecting Rods’. Therefore, unless each one of these parts is individually well balanced, it will vibrate.

Despite, some vibrations are inevitable. These are ‘damped-out’ by flexible ‘foundations’ between the engine/gearbox and the car body. Such foundations are made of rubber fused on metal anchors but in more expensive cars, ‘hydraulic’ foundations have become a norm.

However, even a well designed engine can vibrate if – i) its ‘idling speed’ is below normal, ii) it’s over loaded due to improper gear selection, iii) its foundations are damaged or misaligned, and iv) if one or more of its cylinders is not producing right amount of power compared to others.

Wheels
Until the advent of Maruti-800 in mid ‘80s, concept of ‘wheel balancing’ was unknown in India. A wheel being an ‘assembly’ of its rim, tyre/tube, is invariably unbalanced even when brand new, because of permissible manufacturing ‘tolerances’ of its constituents.

And when the wheel diameters get smaller, their ‘rpm’ for a given road speed goes up compared to larger ones. Given the overall ‘lightness’ of cars nowadays, such unbalance in wheels produces unwanted vibrations in an otherwise ‘smooth’ car. Worse still, it makes the steering ‘wobble’ at higher speeds.

It’s worthwhile remembering that a wheel once ‘balanced’ won’t stay so for long because of daily/uneven wear going on its tyres due to braking/cornering etc. Worse still, the ‘balancing weights’ can and do fall off for many reasons. So it’s advisable to get one’s wheels re-balanced, say, every 5,000 kms.

It’s a popular misconception that only front wheels need re-balancing because that immediately reflects as steering wobble. Since any unbalance in rear wheels also produces vibrations and these, even if not felt as such, do eat into the lives of rear suspension bushes, shock-absorbers AND wheel bearings.

Like wise for Stepney – for simple reason that one may need it any time upfront and if it’s unbalanced, one’ll have a wobbly steering till re-balanced. From this point of view, it makes a lot of sense to have a wheel re-balanced immediately after puncture repairs before stowing away as spare.

A finer nuance to have all the 5-wheels in good balance all the time is that if they’re not, the front ones will inevitably wobble a bit even if not perceptible. Consequently, car’s ‘rolling’ resistance and hence fuel consumption stand to go up!

Conclusion
From the foregoing, it can be visualised that a well tuned engine and all the five wheels in good balance can add significantly to the overall life of a car.