By Sumac
United Kingdom 
My sumac tree hasn't come into leaf as yet it does seem rather late it has had a problem with a thick sap coming from the tree which seems to leave cracks in the bark. This problem has got worse . Do you think it has come to the end of its life it is 14. Years old?
5 May, 2015
Answers
If its oozing thick sap from cracks (gummosis), its likely to become slime flux infection - do as Botanic says and cut it to the ground, or at least below where the problem is. These plants sucker freely and if the roots are healthy, it will regrow.
5 May, 2015
It does not sound good. Can you publish a picture that shows the sap leaking and cracked bark? It is suggestive of a fungal attack.
If (and I mean if) it is dead looking and has 'sap' leaking from it I would cut it to the ground as Sumac coppices/regrows very quickly and some say too well.
5 May, 2015