Citroen C5 Aircross Pistons

Single pistons run R2,150 to R2,300 through our supplier network, which also carries performance alternatives for people building rather than repairing. A full set of four with rings and bearings comes to R9,450 to R14,550 before any labour or machining. That figure is the reason a used engine is always worth pricing alongside — send the engine code and we will quote both.

Blue smoke on start-up, a metallic knock that quietens as the engine warms and the piston expands to fit its bore, and oil consumption past a litre per service. Any one alone is inconclusive; all three together are not. A compression test showing one or more low cylinders confirms it, and a wet test — a little oil in the bore — tells you whether the loss is rings or valves.

A full rebuild with pistons, rings, bearings, gaskets and the machine work to go with them lands at R36,400 to R73,500 through a specialist. A used replacement engine through Pro Citroen Spares frequently costs less and comes with a three-month warranty, which a rebuild of unknown quality does not. On a car worth less than the rebuild, the decision usually makes itself.

The timing of the knock is the clue. A knock that is present cold and disappears as the engine warms points at piston skirt clearance — the piston is rattling in a worn bore until it expands. A knock that is worst hot and grows with load and revs is a rod bearing, which is far more urgent. Both need the sump off at minimum, and the second one should not be driven on at all.

In principle yes, but by the time the head is off, the sump is down and the bores have been measured and honed, you are most of the way into a rebuild anyway. Which is why most workshops bundle bearings and a full gasket set in — the labour is already spent and refusing to replace a R400 bearing shell while the crank is exposed is a false economy. Price it against a used engine before starting.