Bayern fell behind to a Jiri Stajner strike but responded with three goals in 14 minutes to set up an emphatic win and offer coach Jurgen Klinsmann some respite after a mid-week Cup exit at the hands of Bayer Leverkusen.
"We wanted this result," Klinsmann told Premiere television. "We knew we had to put everything into this match and I am delighted that the players did exactly that. It is going to be a tight race to the finish."
Hertha striker Andriy Voronin scored a hat-trick to steer his team to a 3-1 win at Energie Cottbus after the hosts had taken an early lead. The Ukrainian, on loan from Liverpool, has now scored six goals in the last four league matches.
"This was a test of character today," Hertha manager Dieter Hoeness said, playing down their hopes of a first German title since 1931. "We just need to remain focused and disciplined."
Wolfsburg made it five wins in a row with a 1-0 victory against Karlsruhe to move level on points and goal difference with Bayern and newcomers Hoffenheim, who could only manage a 0-0 draw against Werder Bremen.
Hamburg also have 42 points after suffering a 4-1 defeat at Borussia Moenchengladbach, who lifted themselves off bottom spot for the first time since late November.
EXPLOSIVE BAYERN
With Franck Ribery, Luca Toni and captain Mark van Bommel all missing, Bayern were short of options but desperate to win after only one victory in their previous five league matches.
They were briefly shocked when Hanover went ahead after 15 minutes with Stajner's curling shot but were level five minutes later through Daniel van Buyten, who rose above two defenders to head home a Bastian Schweinsteiger free kick.
Miroslav Klose made it 2-1 in the 25th with a another header following an almost identical Schweinsteiger free kick.
Hamit Altintop added a third nine minutes later, with Hanover's defence by now in disarray, when he chased down a Klose header on the right, shrugged off a defender and slotted home.
Further headers from Lukas Podolski and Martin Demichelis wrapped up the win.
