smells bad

hi guys i have been given a creda t/d by a little old dear.
i repaired the thermostat fault and tested it, it works fine now.
but it was heavily stained with grease and fluth now i stripped the whole appliance down and cleanered it out it is actually imaculate no fluff anywhere,
but the problem is when it gets hot ITS SMELLS OF WEE WEE.
does anyone have any idea how to get rid of this smell as i want to sell this machine in my shop
i have taken it to pieces (again) and bleached scrubbed cleanbed all sorts of stuff but still soon as its hot out comes the smell any one got any clues as to what will rid this smell and i would be very grateful