By analysis of the temperature evolution of Raman spectra, we connect an observed supression in low-energy electronic density of states to an anomalous sharpening of the Ba-phonon mode in superconducting YBa2Cu4O8 (Y-124) at around T=150 K. We link the supression of electronic excitations to an opening of a pseudogap. Similar effects observed for the Ba-phonon mode at roughly the same temperature in non-superconducting PrBa2Cu4O8 (Pr-124) suggests that a pseduogap opens up around 150 K also in this material.