Dear 190D22,
I am very sorry but I have a sad story to tell you!
My 300TD turbo - a W124 from september 1990 - a 603 engine did the
same thing as yours.
It started with one or two noisy valves on idling, disappearing at apr.
1000 rpm, temp. climbing to 120 dgC when driving upon steep mountains
in warm weather (30 dgC+), than temp rises to 90 on idle where it was allways on 85 rocksteady.
Than suddenly on a cold start early in the morning, the 603 started very
difficultly with a big - and I mean a REALLY BIG - cloud, bleuish white and
smelly. Once on temp. everything turned fine, except on idle. Than it turned
rough and smoking again.
In the first place I thought it needs new glowing plugs but, when checked, they are all six allright. It was worse.
The cyl. head gasket was gone! The very first sign was a small oil leak from
the 2nd cyl. hydr. lifter into the first cylinder. So it started to be noisy as it
wasn't adjusted automat. anymore. The higher oilpress one higher rpm's
did "cure" this.
Conclusion: a new head gasket! Seen the reputation of the 603's, I strongly
hope there are no cracks in the head!
Lifting it up this weekend promises some moments of suspence...
Come and see next week...
I surely hope your story will end otherwise...
Good Luck,
Danny.

Just wanted to clarify your understanding of the OM60x engines and their associated models.

OM601 - 4 cyl alum head diesel including 190D 2.2 ('83-'85)
OM602 - 5 cyl alum head diesel including 190D 2.5 ('85-'88), 190D 2.5 Turbo ('86-'87), and 300D 2.5 Turbo ('90-'93)
OM603.96 - 6 cyl alum head diesel including 300D ('87), 300 TD ('87), and 300 SDL ('86-87)
OM603.97 - 6 cyl alum head diesel including 350 SDL ('90-'91), 350 SD ('91), 300SD/S350 ('92-'95)

__________________
Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold