Few times now I have had to top off the coolant in the concorde (3.5 aluminum block, 165,000 miles). Had to do yesterday and again today I noticed it was down to the same level in less than 24 hours. No outward signs of leaking anywhere underneath, runs well, no codes and the fuel mileage is normal (not like an oxygen sensor was frosted up from burning coolant). This one has me scratching my head, will be putting it on the rack in the morning and going over the underside to see if its got a leak somewhere where its not dripping directly to the ground. Might pull the intake manifold plenum and see if the inside valley area is questionable and pop the plugs out to have a look around inside. only other thing could be the heater core but even there its not smelling nasty like coolant leaking inside, glass doesnt get slimy and the carpet isnt wet .
Love the car but these stupid little things can really get annoying. Shadow is finally running 100% and now this thing is back for more...