We review the soft X-ray properties of 3C 390.3, 3C 120, 3C 382 and 3C 445, the only broad-line radio galaxies (BLRGs) for which good quality gratings data are currently available. The XMM–Newton/Reflection Grating Spectrometer data of 3C 390.3 and 3C 120 were re-analysed searching for warm absorbers, already discovered in 3C 382 and 3C 445. We confirm the absence of ionized absorption features in 3C 120, but find signatures of outflowing gas (vout∼ 102 km s−1) in 3C 390.3. Its warm absorber (log ξ∼ 2 erg cm s−1, NH∼ 1020 cm−2), similar to that observed in 3C 382, is probably placed in the narrow-line regions. Its gas content is slower and less dense than the accretion disc wind discovered in 3C 445. Independently from the location of the warm gas, the outflowing masses () of BLRGs are significantly (but improbably) predominant with respect to the accretion masses (), suggesting a clumpy configuration of the warm absorber. However, even assuming overestimated values of , the kinetic luminosity of the outflow () is well below 1 per cent of the kinetic power of the jet (Pjet). Thus, the jet remains the major driver of the radio-loud active galactic nucleus (AGN) feedback at least on a parsec scale and beyond. The warm absorber parameters (NH, ξ) of BLRGs span a similar range of values to type 1 radio-quiet AGNs. However, when the mass outflow rate of BLRGs and Seyfert 1s is plotted as a function of the radio loudness, R = log [νLν(5 GHz)/L(2-10 keV)], the mass outflow rate seems to increase with radio power.