As to the revs changing while you release the clutch, this is normal on most modern diesel-engined cars. It's designed to put less stress through the DMF (dual mass flywheel) which is part of the clutch.

Basically, a DMF exists to reduce 'torque shock' from the engine to the gearbox. As you are undoubtedly aware from driving it, your car, like all diesels these days, has really good low-down torque. If that is all slammed straight into a gearbox, sooner or later something will break. So a DMF is fitted to the clutch.

So yes, it could be a DMF problem starting, or a clutch release bearing, or even the clutch itself. You could also try sitting in the car, in neutral, and press the clutch pedal down, and then release it while still in neutral. A person next to the car with their head at ground level may be able to hear any increase in noise - which would indicate that the problem lies somewhere in the clutch assembly, and might help in pinning it down.

As to the fix, if that is the problem, I'm always tempted to say that the clutch, DMF and release bearings should be changed - or definitely the clutch and DMF, with a very close listen to the bearings while out of the car. Simply because most of the work is in the time taken to strip and rebuild, so not replacing parts is often a false economy.

I wouldn't. The DMF absorbs the torque shock from the engine to the gearbox. Take it out, and the weakest thing along the line is the gearbox.

Gearboxes are a lot more expensive to repair or replace.

As above,no way would I be fitting a solid flywheel to this,especially as it has stop/start.This engine has enough problems as it is .No need to make matters worse.You may find that when the box is out,the dmf is serviceable.

I understand the arguments re DMF/SMF however this engine is at lower end of the tourque / power spectrum so would probably be OK with a SMF. However the DMF was fitted for a reason!

It's obviously a popular conversion as all the major parts suppliers seem to automatically quote both now!

What I don't underderstand is how stop/start affects this. Your engine will only restart when you push you clutch pedal to the floor. When you release the clutch the engine will already be running.

Agree with comments above to replace ALL clutch components whilst gearbox is off the car - the biggest cost is the labour to remove/refit. At least this version shouldn't be fitted with the concentric slave cylinder (if it is - change this as well!)

Edited by Big John on 17/10/2015 at 11:14