Find out how the computer is situated. If within a foot of a wall at the back, or in a corner of the room, the exhaust air from the case can be sucked back into it.. raising temps quickly. Best is having more than 2 ft. space behind the case.. even more. If not practicable, then fashion a diverter out of a small thin box, to direct the exhaust either up or sideways. An empty macaroni box or similar would work well. Remove the top, cut out one side hole (where the exhaust fan meets). A bit of duct tape holds it in place.
Sounds too simple, but does work wonders!
True, almost all PC cases have no provision for adequate front vents. A custom auto body shop might be able to do a series of small louvers in the side panels, if desired. Otherwise, a 6" fan opening in the service panel side would provide proper cooling. But it would need a metallic screen guard to avoid excess RFI emissions.
If there is also a rear case fan, it should push air into the case.. not draw out. Otherwise, the PSU could be restricted of its cooling air flow. The ideal ratio of air flow in a PC case is 1.5:1 inlet versus outlet. This helps keep debris out of the optical drives.
F@H.. to solve mankind's maladies.. in our lifetimes!