Cliftonville won a thrilling semi-final to keep alive their hopes of a third consecutive League Cup success.
David McDaid's shot went in off Bangor's Thomas Wray for the opener on 33 minutes and Jay Donnelly added the second but Barry Walsh replied for Bangor five minutes before half-time.
A Tomas Cosgrove own goal brought the sides level, then a superb right-foot shot by Joe Gormley made it 3-2.
Paul McDowell's chip restored parity but Gormley nodded in after 75 minutes.
The Reds dominated the opening period at Solitude, and squandered several chances as Bangor, conquerors of Crusaders in the quarter-finals, struggled to keep pace with their Premiership opponents in difficult wet conditions.
Ronan Scannell's shot drifted wide of the right hand post, Jay Donnelly headed wide when left unmarked in the area and Gormley had a right-foot drive saved by Paul Cairnduff.
On-form home striker Gormley also shot over and Cairnduff palmed a fierce McDaid effort onto the bar as Tommy Breslin's side continued to lay siege on the Seasiders' goal.
McDaid's powerful delivery from the right went in off defender Wray for the first goal, while three minutes later Donnelly fired in the rebound after Cairnduff spilled the ball and then received lengthy treatment on a knee injury, before coming off.
Walsh gave the visitors some hope when he swept the ball into the bottom corner of the net following the Championship One side's first attack of the game at the conclusion of the first half.
Bangor upped their game significantly after the break, with Conor Devlin diving low to push round Andy Morrow's first-time shot, Jordan Forsythe seeing his header cleared off the line by Martin Donnelly and Mark Cooling firing over the top.
Cosgrove appeared to get the final touch from an Andy Hall free-kick under pressure from substitute Richard Gibson on the hour, before McDaid was off-target with a strike when well placed.
Four minutes later Gormley's thunderbolt from outside the area went in off the post, while soon after a similar effort by the prolific forward was pushed away by substitute goalkeeper Darren Gibbons.
Garth Scates's side displayed their fighting qualities as they responded yet again, McDowell chipping the ball over Devlin as he came off his line.
Gormley nodded in the winner with 15 minutes remaining after Gibbons made an initial save from Jude Winchester.