Free Automotive Repair Advice by Certified ASE Technicians
Diagnostic Testing /
Check Engine Vacuum
Testing Engine Vacuum
An engine generates vacuum when running, this vacuum is used to operate several
accessories from the temperature control system (heater, air conditioner) to the
cruise control. Testing a vacuum source is simple, remove the vacuum line from any
giving accessory and attach the vacuum gauge. Start engine and allow to idle, the
gauge should read between 14 and 18 inches of vacuum. If a low or no vacuum exits
there is blockage or breakage of a vacuum line. Inspect all vacuum line integrity,
then remove vacuum line from the engine source and check for blockage, repair as
needed and recheck the system.
Engine Vacuum Test Kit
Removing Air from the Brake System
Most vacuum test kits are produced with a brake system bleed attachment. Once
the brake bleeder is open attach the vacuum hose over the end of the bleeder fitting.
Then use the fluid storage container inline to the hand vacuum pump. Operate the
pump until no air is present in the line. Remove bleeder hose and tighten the bleeder
fitting. Refill the master cylinder reservoir with brake fluid as needed.
Diagnostic Testing /
Check Engine Vacuum
Check Manufacturer Specific Engine
Vacuum Test Questions and Answers
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