Not sure but i think the glow plugs are activated during a regen attempt to increase in cylinder temperature but not 100% sure on that.

There is a post (I think its about a Renault) which describes the use of glow plugs during a regen process.

I've already removed the manifold which wasn't that bad although the bolts fort he manifold flap motor isn't the easiest to access other than that not to bad.

When i have time i'll reassemble and start again.

Still don't understand where the oily substance can come from, i thought it could be antifreeze at 1st but i tested with a refractrometer and it stayed at water line. Can't see the exhaust temperature burning the antifreeze away and jsut leaving water.

thanks
lee