Chrysler laser 1990 Technical Information Manual page 238

Hump phenomenon specific to viscous couplings
Rotating speed difference
Hump is a phenomenon specific to viscous couplings althob,, I
it does not occur under normal operating conditions.
This phenomenon occurs when the silicone oil temperature has
Transmitted
risen due to sustained differential action. Normally silicone oil
torque
fills the space between the inner and outer plates, preventing
their direct coupling. When silicone oil expands at a high
temperature to such a degree as to develop abnormally high
pressure between the plates (normal thermal expansion is
Temperature
absorbed by compression of air mixed in silicone oil), silicone oil
escapes from between the plates. As a result, the plates
couple directly, causing abrupt torque transmission. When the
viscous coupling is directly coupled in this way, a rotating
'II I
speed difference does not exist, and then silicone oil tempera-
ture drops and normal function is restored.
Hump mode
Hump mode