how do i change the glow plugs on a citroen zx 1.9 TD

You need to remove the intercooler from the top of the engine, unclip the plastic surround first, then u will see 3 (i think) 13mm bolts at the back of the cooler & theres 2 10mm bolts holding the front of it in place. Loosen the hose clip & unclip the throttle cable from the cooler & lift it away, do not lose the intake manifold rubber seal that should still be attached to it. Remove the 4 8mm nuts from the heater plugs & remove the link wire. Remove the 4 heater plugs with a 12mm deep socket/universal joint/swan neck spanner depending on which one u r removing. No is 1 + 2 (the 2 nearest the flywheel) should be easy to get to with the socket, no is 3 + 4 r more difficult, no 3 is not bad with the spanner but if ur car has the larger type Bosch fuel pump as opposed to the small Lucas pump then no 4 is a sod to get to, use the swan neck spanner & just persevere. It may be worth putting a little copper grease on the threads when fitting the new ones. When refitting the wires do not overtighten the nuts as the tops of the glow plugs can be a bit fragile. Also do not overtighten the 13mm bolts on the back of the intercooler as it is easy to damage the threads in the manifold.