Ben and his son Samuel were cruising in his 1969 Cadillac DeVille Wednesday -- where temps hovered around 90 -- when the car apparently started smoking.

Ben pulled over, popped the hood and hit the pavement in search of a gas station to buy coolant.

Ben eyed the engine, looking for the radiator, and a passerby leaned in for an assist. As Ben hydrated his ride, someone couldn't resist taking a selfie with him.

This isn't the first time Ben's had car issues with his son ... Samuel jumped into the driver's seat of a Lamborghini last year while car browsing with his dad in Bev Hills, but things took a turn for the worse when Sam put the car in reverse, backing into a BMW.

And then there's the time last year when Ben failed to navigate a Starbucks sign at the drive-thru while J Lo rode shotgun.

And speaking of J Lo ... she had her own issues Wednesday when she got locked out of a gym. She was clearly more upset than Ben, telling photogs, "F**k you, bye."