Karim Benzema, captain for the day, put Madrid ahead after 12 minutes before before Toni Kroos doubled the advantage just before half time at Valdebebas. Ferland Mendy thought he had made it 3-0 just after the hour mark but it was ruled out for offside following a VAR review.
Victory for Zinedine Zidane's men was enough for them to leapfrog Barcelona, who hammered Alaves 5-1 on Saturday, with Madrid gaining some momentum ahead of their Champions League clash against Atalanta at the end of the month. Leaders Atletico Madrid are five points clear and with two games in hand on Zidane's side.
The only negative from the afternoon came when Dani Carvajal limped off with an apparent hamstring injury.
With Atleti, Barcelona and Sevilla all on relentless runs of form, Kroos said Real could not afford to drop any more points if they wanted to keep up with the pacesetters.
"The others just keep on winning so we have to try and do the same. If we want to have any chance of staying at the top we have to win all our games," he said.
"Every game we play we always try to win that's all we can do, it's what everyone else is doing so we have to try and do it too. We're worried about the injuries as we're missing some very important players but there's not much we can do about it."
Real were without seven players due to fitness issues and midway through the first half they lost Carvajal to yet another injury on his return to action, taking the total number of injured defenders in their squad to five.
Yet even without some of their most influential players, including Sergio Ramos and Eden Hazard, they proved far too strong for Valencia, who had to make do without coach Javi Gracia on the sidelines due to a touchline ban.
The visitors missed their coach's presence as they played with barely any urgency or ambition, particularly in a lifeless first half in which they failed to register a shot on goal.
"We're left with a terrible feeling as we gave away the first half," said Valencia captain Jose Gaya, whose side thrashed Real 4-1 at home earlier in the campaign.
"It's not the first time this has happened this season and if we don't improve we won't get the results we need. We were better in the second half but overall we didn't show the intensity a game like this demands. We made it too easy for them."