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Replacing pistons

Question : AFTER a breakdown, my 1999 Proton Wira had to be towed to a workshop which later reported that the vehicle had a cracked piston that must be replaced.

I have been told that it is not a good idea to replace a single piston but, instead, should replace all four as a set, and to carry out a complete engine overhaul at the same time, at a cost of about $4,000.

I would appreciate your advice on whether all this work is really necessary.

Answer : THE amount of work required depends very much on the mileage that the vehicle has travelled, as well as the amount of internal damage that has occurred.

In reply to your first query, it is commonplace that pistons are sold as a complete set, rather than as singles, since it is imperative that there is a limit to the weight difference between pistons in order to maintain engine balance.

Engine imbalance results in vibration and premature wear of some components. Although pistons used to be available from vehicle manufacturers or from third party component suppliers as singles, these are becoming increasingly scarce.

The work and time required to replace a single piston is not much less compared to a complete engine overhaul.

If the engine has already done a substantial mileage, say in excess of 100,000km, it is probably advisable to do a complete overhaul since the additional costs involved would encompass machining work such as grinding of the crankshaft journals, and boring of the cylinders.

In addition, you would also require new sets of main and connecting-rod bearings. An overhauled engine is capable of covering as much mileage as a brand new engine.


Replacing pistons


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