Citroen C4 Slipping Clutch?

Presumably the clutch pedal is able to move freely into the 'fully engaged' position - eg there aren't any mats, feet, luggage, or other things touching it, or stiff linkages or weak springs or dodgy hydraulics anywhere?

The clutch pedal is able to move freely. There is nothing in the way of the pedal becoming fully engaged.

Just about the easiest way to check if the clutch is slipping is to start off in 1st gear and release the clutch pedal fully then accelerate as hard as the car can. If the clutch is slipping the engine revs will climb whilst the car will not gain speed, or will not gain speed as quickly as it should. Easing off the accelerator again will result in the engine speed dropping until the clutch starts to bite again when the car will slow down.

You can't reliably tell if the clutch is slipping, or not, unless the pedal is fully released (and your foot is not resting on it). This is particularly true if the biting point is near to the top of the pedal travel.

HTH

I have a C4 but just the 1.6 petrol. Do as SteveG suggest but use a steep hill to try it out. With your foot off the clutch pedal creep forward then floor it, you should feel the pick up and a hill will perhaps give you a better idea if it is slipping or not.

Neil