This paper discusses a method for fault detection and isolation (FDI) in co
ntinuous dynamic systems. A key aspect of this approach is the coupling of
a qualitative diagnosis engine and a monitoring system that computes symbol
ic feature values through a signal-to-symbol transformation on the continuo
usly sampled measurement data, Signal analysis techniques with a sound stat
istical basis are employed to generate reliable symbolic data. The methodol
ogy is evaluated on the diagnosis of engineered faults in the cooling syste
m of an automobile engine that has been instrumented with temperature and p
ressure sensors. Results show the interdependency between modeling for diag
nosis and the feature extraction system.