Can an overdose caused by taking to much Coumadin (warfarin) cause some kidney damage?

Rarely. The biggest problem with an overdose of Coumadin (warfarin) is the blood being too thin and you being at high risk for bleeding. There are a few cases (rarely) where patients have had hemorrhage (bleeding) in their kidneys from high Coumadin (warfarin) levels causing kidney damage.
Not directly. Warfarin (generic name for coumadin) works by affecting the production of proteins in the liver. Overdosage can lead to bleeding - I am not aware of any direct renal toxicity of warfarin but would recommend doing some research online.