It's unfortunately a very common problem with the Mercedes OM642 engine. There are improved (purple) oil seals that are supposed to be a cure. It happens on Mercedes models that are fitted with the OM642 diesel as well as our Gen 1 CRD 300'sOh, hadn't come across this issue before!
Does it affect all 300C or just a particular engine?
Something else to worry about...
Cheers for that, only issue is I'm not on Facebook and have no intention of joining that horrific organisation Don't suppose you have any other means of contacting him or could contact him on my behalf?Might be worth traveling. Join the UK 300 group on Facebook (Link) and ask for Gavin Bailey. Think he's somewhere Wiltshire way, he's done multiple people's oil cooler seals (I don't have person experience). Might be worth looking him up?
It's a full day's job (8 to 10) hours and Gavin is the only person I've heard recommended for this