I took it into a fairly respected independent shop today (better known for bmw's than benz's), and they took a listen for the rattling, they felt it is coming from the inside of the engine somewhere. Said it could possibly be related to the timing chain, or something they called a "vanos" - related to cam timing. They said it wouldn't be worth getting in there to investigate since it would take a lot of labour.

I'll take a look at the resistor mod as well to lower the trigger temp for the aux fans. At the shop today we also some small signs of coolant residue around a couple of hoses where they meet the radiator. Again, radiator was replaced, but it seems like there might be an issue with coolant flow somewhere..

Shop also pointed me to some signs of oil seepage from the valve cover and suggested I get the seal replaced. I could also see evidence of the oil on a couple of parts nearby, not too bad, but I will get it done.

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1993 300CE