Car is a 95 W124 E300D with 155k miles.
I have just replaced all 6 glow plugs to fix a starting problem. That is now fixed but the idle when cold (only very cold - icy mornings) is uneven - the revs hunt between 550 and 700 rpm. it is not very serious does not stall but it is annoying. Once warmed up it is fine. Starting from hot and cold is also good - as soon as the key is turned.

There are a number of other observations but dont know if they are linked.

When starting from stone cold there is a very slight hesitation in the turning over of the engine - bit like a slightly discharged battery - but the battery is 6 months old Bosch unit.
There is air in the diesel supply pipe leading to the fuel filter.

Any ideas?

Thanks