Your car or truck relies on engine vacuum for a lot of applications, on things ranging from HVAC doors and pop-up headlights to critical vehicle systems like your power brakes and ignition timing.
While most engines naturally create adequate vacuum, if your vehicle has a diesel or small-displacement engine, then there’s a good chance it has an auxiliary vacuum pump to create additional vacuum pressure to operate those aforementioned systems and components.
Note: A long-duration camshaft with increased overlap can decrease engine vacuum as well, which means you’ll often see a supplemental vacuum pump installed on a high-performance engine.
Problem is, a bad vacuum pump can cause symptoms that are often improperly diagnosed as other issues—we’re talking things like a hard brake pedal, a check engine light, and rough idle.
The fine folks over at Cardone Industries made this helpful video to show you some common indicators of vacuum pump failure and, more importantly, show you some quick and easy diagnostic measures to nail-down improper engine vacuum as the culprit.
Better still, all you’ll need to perform the test is a simple vacuum gauge and a few minutes to measure your vacuum at an unplugged vacuum hose.
It’s an easy troubleshooting procedure and could potentially save you a lot of money by thwarting an incorrect diagnosis.