I thought the head and/or gasket took a poo on my SDL recently due to the excessive coolant use. Well I decided to take a good look at the entire cooling system before going further.
Rad hoses were okay, rad okay, water pump okay, etc. Well... back in June I had flushed the system out of that crappy green coolant. I then went to check all the hoses behind the firewall around the monovalve and such... turns out I had forgotten to fully tighten the hose between the head and the firewall.
Boy do I feel like a big fool!
I gave it a good shakedown yesterday and today while picking up a 240D with another member here. Coolant temp is perfect, sits just a tad over 80°C. Time to finish the A/C up on there now!