  To put new constraints on the r-mode instability window, we analyse the
formation of millisecond pulsars (MSPs) within the recycling scenario, making
use of three sets of observations: (a) X-ray observations of neutron stars
(NSs) in low-mass X-ray binaries; (b) timing of millisecond pulsars; and (c)
X-ray and UV observations of MSPs. As shown in previous works, r-mode
dissipation by shear viscosity is not sufficient to explain observational set
(a), and enhanced r-mode dissipation at the red-shifted internal temperatures
$T^\infty\sim 10^8$ K is required to stabilize the observed NSs. Here, we argue
that models with enhanced bulk viscosity can hardly lead to a self-consistent
explanation of observational set (a) due to strong neutrino emission, which is
typical for these models (unrealistically powerful energy source is required to
keep NSs at the observed temperatures). We also demonstrate that the
observational set (b), combined with the theory of internal heating and NS
cooling, provides evidence of enhanced r-mode dissipation at low temperatures,
$T^\infty\sim 2\times 10^7$ K. Observational set (c) allows us to set an upper
limit on the internal temperatures of MSPs, $T^\infty<2\times 10^7$ K (assuming
a canonical NS with the accreted crust). Recycling scenario can produce MSPs at
these temperatures only if r-mode instability is suppressed in the whole MSP
spin frequency range ($\nu\lesssim 750$ Hz) at temperatures $2\times
10^7\lesssim T^\infty\lesssim 3 \times 10^7$ K, providing thus a new constraint
on the r-mode instability window. These observational constraints are analysed
in more details in application to the resonance uplift scenario of Gusakov et
al. [Phys. Rev. Lett., 112 (2014), 151101].
