How to check engine vacuum hoses

Written by dan ferrell
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When you look under the hood of a vehicle, you'll see what seems to be an intricate highway of hoses connecting different points of the engine to electronic, plastic and weird-looking metal components. But this web of vacuum hoses, lines and tubing is an integral part of the engine. The vacuum system provides a lower atmospheric pressure and basically transforms a car engine into a huge pump that sucks air, mixes it with fuel and expels it along with combustion gases. So even light damage to one of those vacuum conduits can cause all kinds of performance problems--from a rough idle to a non-starting engine. The following steps will simplify the job of checking all those vacuum lines and making sure they are in good shape.

Skill level:

Things you need

  • Utility knife

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  1. 1

    Locate the Vehicle Emissions Control Information (VECI) label. You can find this small white label under the hood, in front of the radiator, on the firewall or on either side of the engine compartment. It provides a simple diagram of the vacuum hoses in your engine and the components they connect to.

  2. 2

    Follow each vacuum hose, line and tube, using the VECI label as a guide. Inspect the entire length of the hose and special connectors. Detach and replace vacuum hoses one at a time for inspection when necessary.

  3. 3

    Take note of the routing when you remove a vacuum hose for inspection, so you can replace it the same way.

  4. 4

    Run your fingers along the hose and feel for breaks, cracks, kinks and chafed, swollen spots that might leak or obstruct the vacuum. Make sure the inside of the hose is free of sludge, oil or foreign matter. Clean a hose or replace it with a new one when necessary.

  5. 5

    Check the tips of rubber vacuum hoses for distortion or hardening. A vacuum hose that does not fit tightly over a connector or fitting is prone to leaks, and may cause engine performance problems.

  6. 6

    Trim the tip of a hose using a utility knife if it does not fit tightly over a fitting. Make sure the rest of the hose is in good condition.

  7. 7

    Make sure every vacuum hose, line and tube is clear from hot engine and oil-covered components, which could damage or degrade the vacuum conduit. Use nylon cable ties to reroute vacuum hoses if necessary.

Tips and warnings

  • If the VECI label on your car is missing, you can buy one at your local dealer. You may have to provide your vehicle’s VIN number, make and model.
  • When replacing a vacuum hose, make sure the new one is of the same type as the old. Some vacuum hoses are designed to withstand higher temperatures; others may feature a different wall thickness.

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