Ask the mechanic: How should I prepare for a long journey after prolonged parking?

Hello Paul, I have a pre-millennium Toyota Prado 3.0 diesel turbo that just goes on forever. Even after 300,000kms, it starts first time every time, goes well and does not belch smoke or burn oil. However, in recent months, I have noticed a slight reduction in power and an increase in fuel consumption, even after its regular service. Is this irreversible old age, and/or is there something I can do to extend its life and restore its performance? Jack

All vehicles suffer progressive loss of performance with age, through engine wear which reduces compression and the gradual degrading of other components in the system in a number of places along the whole drive train. The effects may have only just become noticeable to you, but they have been happening to some degree for much of your car’s life. If your car is used moderately and serviced diligently, it might continue to go well (though less-and-less optimally) for many more years as this ageing process continues. With an increasing number of repairs and some replacements, half-a-million kilometres is not unthinkable for cars like yours. Meanwhile, you could give it some 300,000km birthday presents to help it feel younger. 

If it is not burning any oil and the exhaust does not have a hint of grey smoke when the engine is revved hard, the chances are the piston rings are in good enough condition, but you could have the compression tested to be sure. If it is not belching black smoke, there is probably nothing seriously wrong with the injectors, but fitting new injector nozzles could perk up the power and improve fuel economy. Injector overhauls and re-setting are best done on a professional test bench.

It is also worth ensuring the engine is “breathing” properly; a new air filter if the existing one is well used, and also a check and cleaning of the insides of the intercooler, which may be fouled with dirty oil, therefore restricting air flow. Prados also recommend a precautionary change of the timing belt at least every 100,000kms. Yours is due its third. Even if the belt is not about to break, chances are it has stretched slightly and no longer delivers the precision for optimum performance and fuel economy. Think, too, about when you last changed all the oils/fluids in the gearbox, the diffs, the power steering and the brakes. If you cannot remember when, add those to the birthday libation.

None of these measures will give a venerable old car the same performance as a new one, but they will help wind back the clock and help keep it ticking longer into the future.

If a compression test shows the piston rings are worn (experienced mechanics can also spot other clues) a “short engine” overhaul might cost up to 10 percent of the vehicle’s value, but it will give an old engine a new lease of life.

The principles apply to all turbo diesels and, in diverse ways, to all old cars.

What causes my Raum to consume a lot of fuel and emit white smoke?

Hello Paul, I drive a Raum old model 90s but it emits white smoke from exhaust and its fuel consumption is costly. From Kakiri in Wakiso District to Industrial Area in Kampala, I use fuel worth Shs50,000. Please advise. Timothy

Hello Timothy, high fuel consumption and white smoke suggest some form engine inefficiency. To start with, confirm that the colour of smoke is white not greyish black. White smoke is usually a condition where an engine leaks coolant internally due to a bad cylinder head gasket. This leads to burning both coolant and a fuel air mixture. 

This will lead to reduced engine performance and poor fuel economy. There are situations when your combustion chambers can be flooded by unregulated amounts of fuel, more than can be burnt. The unburnt fuel is emitted through the exhaust as smoke. This can be a result of a faulty ignition system (bad coils or spark plugs) which fails to burn fuel efficiently or a faulty fuel delivery system (bad fuel injectors or injector circuits) which cause delivery of unregulated fuel amounts. Have these areas investigated to resolve the situation.

Why does my car transmission jerk when I slow down

My car jerks only when slowing down from any speed and when it gets to 40 mph exactly. I am thinking maybe shifting gears or transmission is the cause?  Juliet

Hello Juliet, it is normal for a car conventional automatic transmission to jerk slightly when shifting downwards as you slow down. However when the jerk becomes more noticeable or violent, it should be investigated. A computer diagnosis is a good first step to make sure there are no electrical solenoid faults.

Thereafter, check the level and condition of transmission oil and service it to make sure you have the correct level and best condition of oil.