I couldn't tell or either missed it, but are these new hoses?? I kept having leaks on my upper radiator hose. Swapped in another used spare hose I had. It leaked too.
I installed a new hose and my leak has vanished!
I've had to replace a similar hose as the "U" shaped one you have on one of my 240's, so sometimes old hoses just cannot be sealed.
Of course all this is moot if you're using new hoses.
RTV ain't the solution, you will be just temporarily masking a real problem.....

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John