| 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. |
