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Grumpy old new cars - Part I Mechanical

words - Joe Kenwright
With the help of a local licensed vehicle tester, Joe Kenwright uncovers the mechanical traps waiting to catch hapless owners as the modern car leaves the warranty period.

One of the best ways to increase reliability while cutting costs is to reduce the number of parts and integrate as many as possible in a single unit that can be fitted on the production line in one easy movement. The downside is that the owner can be left to replace whole sub-systems when even a tiny component fails.

Engine Computer
These automotive versions of your home computer dictate how well your engine and transmission run. Because they can also dictate whether the car runs or not, they are usually part of the security system. Gone is the old fashioned coil and points ignition system and in its place is a series of electronic devices that communicate with the engine computer (ECU). One of these devices is called a coil pack which supplies the spark. Some cars have several coil packs.

The ECU will normally tell you if a coil pack is faulty but in one of Australia's biggest selling small cars, the computer will tell you that the coil pack is causing an engine miss when the computer itself has failed. And then the big bills start rolling in. After you spend $400 fitting a new coil pack, you soon find that the coil pack is non-returnable and the problem is still there. At that point, you or your local garage are cut out of the repair.

A replacement computer can only be programmed by the manufacturer. You usually can't fit a secondhand one because they are designed to shut down as soon as they are pulled out of a car. You will then need to spend $1500 to buy a new one plus a fat programming fee to make it work in your car. By the time you have fixed what started out as a simple engine miss in a car that has done as few as 60,000km, it can easily cost you $2000.

Electronic Distributors
It was very common in the 1990s to integrate the coil, distributor and the crank angle sensor in a single unit that cost $1200 or more to replace even if only one function fails. Because these delicate electronics are mounted on the engine, they get too hot in Australia and can fail earlier than expected especially if the seals separating them from the engine oil fail and drown them in oil.

Clever technicians have learnt how to carefully pick them apart and fix the failed component and re-assemble them. Before replacing one of these big budget items with expensive new parts, check around to see if it is happening often enough for someone to make a tidy income offering a cheap changeover unit.

Body Control Modules
These control all the slick functions like intermittent wiper dwell, courtesy light delay, instrument lighting, some power window operations, door locks and others plus they can also be linked to the security system and engine computer. When they fail, you can lose a large range of cabin functions and some engine or transmission functions. Like the ECU, you may not be able to use a cheap secondhand one because it needs to be programmed to your car by the manufacturer. Costs are similar to an ECU for a cost of over $1000 and that is providing the manufacturer still stocks one. Again, you might be better off looking for someone who has worked out a way of accessing it and fixing it.

Alternators and Batteries
It is not unusual for the voltage regulator function in a modern alternator to suddenly go haywire and send three or four times the normal voltage through the electrical system. If you don't pick up the funny sequence of warning lights that flicker on when this happens and shut down immediately, you will face a damage bill that will make your eyes water.

In the old days, batteries were hefty enough to stop most of this voltage getting through but today's light batteries provide little resistance. In a car like the Mazda MX-6, this surge will take out the ABS computer, climate control module, airbag module, engine management computer, four wheel steering control, security system, sound system, instrument panel, body computer and all switches that have a delay computer. Total cost? Over $10,000 in parts alone plus labour to access them plus battery plus alternator. At this point, you start praying that someone has smashed your model up but left the computers still working.

Even if the alternator doesn't fail, you can invite the same damage if you use jumper leads to hook up to another car with a failed battery. There is an even chance that the other car's battery will have failed because its alternator was overcharging it and it is now ready to send the same spike through your electrical system. Do NOT even think of jumpstarting another car unless the jump leads have surge protection.

Cam Belt Water Pumps
Someone had the bright idea of hiding the water pump then using the cam belt to drive it. Problem is that if the water pump fails and breaks the belt, you can destroy the whole engine. Or if the water pump fails and drops the coolant, you can cook the engine without ever seeing the early warning coolant leaks. After the cam belt is changed, it is almost certain that the extra tension of the new belt will cause the water pump to fail a week or two later.

Good mechanics have learnt that replacing the water pump, cam belt and tensioner all at once is much cheaper than doing the whole job again two weeks later when the pump fails. Hondas are particularly notorious for this.

Electric Fuel Pumps
In the old days, a fuel pump sucked the fuel up to the engine then kept a fuel chamber topped up with a system that closely replicated the cistern in your toilet. Today's systems rely on high pressure electric fuel pumps that constantly circulate fuel from the tank to the engine then back to the tank ready for the engine to draw off a high pressure stream as needed. These pumps get hot and are submerged in the tank to keep them cool. The cool stream of petrol constantly flowing through them also provides vital cooling.

If you run your tank on empty, the remaining fuel gets too hot which eventually kills a very expensive fuel pump that can cost serious money to access on some cars. Low fuel levels also increase the risk of feeding water and rubbish trapped in the tank into the pump. This is why fuel pumps often fail a month or two after you run out of petrol. Treat quarter full on your gauge as empty or else.

Aluminium Radiator and Heater Cores
Lightweight aluminium radiator and heater cores offer big weight and efficiency advantages. However, the coolant that is meant to protect them can start eating them after two years which is why the coolant change intervals are as important as oil changes. For certain model years, even the best cars had unreinforced plastic hose connectors attached to these aluminium radiators and heater cores which harden with heat and age then snap off.

While exchange units are reasonably priced, accessing a heater core is a nightmare job on any car. In too any cases, owners are cooking their engines after these plastic connectors fail because the temperature gauge no longer works once the coolant escapes.

Catalytic Converter
They blame Aussie fuel but the cat converters on many expensive European cars are breaking up inside prematurely for a replacement cost of $2-6000. What price clean air? Find a clever metal worker who can split the cat open and fit local parts inside.

Electric Power Steering
Small cars are switching to power steering driven by electric motors, not the engine. Their control systems which are heavily computerized are generating glitches and failures. To repair simple oil leaks for a roadworthy certificate, the engine now has to be removed to access vital steering components.

Space Saver Spares and Run Flat Tyres
Neither have any place in Australia especially when they are most often fitted to cars best driven outside city limits. Picture having a puncture when it is wet and late at night, the car is fully loaded and you are least a 100km from civilization. Most of us have been there.

The tiny space saver tyre then turns the trip into a tediously slow and dangerous one while your accommodation is booked out to someone else and your passengers are left filthy from nursing the full-sized flat tyre. Now the trend is no spare at all. It is a common topic amongst motoring journalists about how far you would get in Australia's remote regions before a punctured run flat tyre and its rim were destroyed. Then the talk turns to how far your car would need to be transported to be repaired or how much of the car will still be there by the time you find someone to retrieve it - all because there is no spare tyre!

Low Profile Tyres
Almost as useless on many Australian roads as a space saver, these tyres leave so little rubber between rim and road that a high speed meeting with a pothole can generate $2000 worth of trashed rim and tyre.

It also comes as a shock to many owners that a V or Z-rated tyre can wear twice as fast as your average tyre because of the softer, grippier rubber and the replacement cost can be six to ten times the normal cost.

Thanks to Frank's Auto Service Centre (03) 9499 6481.

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Published : Wednesday, 1 October 2008

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