After an uneventful opening 13 minutes, youngster Danny Glover showed what an asset he could prove in League Two when he burst into the area and fired a powerful shot that flew inches over the crossbar.
The visitors look the lead in the 25th minute when Adebayo Akinfenwa played a clever backheel inside the box to find Ryan Gilligan, who coolly slotted the ball into Chris Martin's bottom left corner.
A second was added to only two minutes later when Jason Crowe's hanging cross from the right was met perfectly by Andrew Holt, who thumped the ball past Martin and into the back of the net.
The Valiants struck back after half an hour when Glover mimicked Crowe's earlier run to set up strike partner Marc Richards, who turned quickly to lash the ball into the roof of the net from close range.
Vale could have easily added two more to their tally, but Town had the woodwork to thank on both occasions with Luke Prosser and goalscorer Richards heading against the frame of the goal.
The home side burst out of the traps and were on level terms four minutes after half-time when Richards headed Keith Lowe's throw-in into the path of Glover, who finished superbly with a left-footed volley from 15 yards.
The Cobblers almost edged ahead 11 minutes from the end when Giles Coke made a lung-bursting run from the halfway line, but young goalkeeper Martin made an impressive save to stop him in his tracks.
With only a minute left on the clock, Sinnott threw caution to the wind by introducing two more youngsters, but it was Northampton who pushed on, trying in vain to find a late winner.