Citroen Relay Valves

One cylinder misfiring consistently, and that same cylinder reading low on a compression test. Around it you get lost power and a rough idle, and a burnt exhaust valve will often whistle under load. Confirm it with a compression or leak-down test rather than by ear — either way the head has to come off to put it right.

In practice a single valve is never just a single valve: the head comes off and gets inspected properly, so labour carries the bill. Valves and head parts for Citroen come through our supplier network. Send your engine code via the form and we will quote the full head refurb rather than a part-only figure that will not survive contact with the workshop.

Nearly always a timing chain or belt failure — the pistons hit the valves when timing goes out of sync. On the 1.6 HDi and 1.6 THP engines, a stretched chain jumping teeth is the usual cause. Catch cold-start rattle early and you avoid bent valves entirely.

Gently and briefly, yes — though you will feel it in performance, economy and emissions. As a way of life, no. Combustion gas escaping past the valve overheats that cylinder and goes on to damage the piston and the catalytic converter. Get the head off inside a week or two.

Two methods: a compression test reveals a low cylinder and a cylinder leak-down test confirms whether leakage is through an exhaust valve (hissing from exhaust), intake valve (hissing from intake) or head gasket (bubbles in coolant). Both need a warm engine.