How to Know When to Replace a EGR Valve

Written by dan ferrell
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How to Know When to Replace a EGR Valve
A Saab engine EGR valve. (Photo courtesy of MH at Wikipedia.org.)

The exhaust gas recirculation (EGR) valve is an important part of your vehicle emission control system. The valve introduces a certain amount of exhaust gases into the intake system to help reduce harmful emissions. On vacuum type valves, the passages may become clogged with carbon deposits or the diaphragm may develop a leak, in which case it needs to be replaced. Follow these steps to test the EGR valve on your vehicle and replace it if necessary.

Skill level:
Moderately Easy

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Things you need

  • Small mirror
  • Phillips screwdriver
  • Hand vacuum pump
  • Wrench
  • Ratchet and socket
  • Ratchet extension
  • Scratch awl
  • Plastic scraper
  • New EGR gasket

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Instructions

    Testing the EGR Valve

  1. 1

    Apply the parking brakes and set the transmission to manual or park.

  2. 2

    Turn on the engine and let it idle. Wait about four minutes to bring the engine to operating temperature.

  3. 3

    Open the bonnet and locate the EGR valve. The valve is a round, metal component, similar to a flatten mushroom, between two and three inches in diameter. It usually sits around the top and to one side of the engine. Depending on vehicle model, it might have a vacuum hose and an electrical connector plugged on top. A metal pipe connects the bottom of the valve to the exhaust manifold.

  4. 4

    Remove the air intake assembly, if necessary, to get access to the accelerator linkage.

  5. 5

    Raise engine speed to 2,500rpm very quickly by operating the accelerator linkage by hand. Watch the stem inside the EGR valve and make sure it moves as you accelerate the engine. You might need a small mirror to watch the stem from the bottom of the valve. If the stem does not move, the valve might need cleaning.

  6. 6

    Disconnect the vacuum hose from the top of the EGR valve and plug the hose using a Phillips screwdriver of the appropriate size.

  7. 7

    Connect a hand vacuum pump to the vacuum port on the valve.

  8. 8

    Apply 15 in-Hg of vacuum to the valve with the engine running. The engine should idle rough or even stall. If the stem moves but the idle does not change, there might be a passage restriction. If the diaphragm inside the valve does not hold vacuum, replace the valve.

  9. 9

    Turn off the engine.

    Cleaning the EGR Valve

  1. 1

    Disconnect the vacuum hose from the top of the valve.

  2. 2

    Unplug the electrical connector from the top of the valve, if your particular model is equipped with one.

  3. 3

    Loosen the pipe nut, between the exhaust pipe and the valve, using a wrench.

  4. 4

    Remove the two EGR mounting bolts using a ratchet, ratchet extension and socket.

  5. 5

    Lift the valve off the engine compartment and discard the gasket if equipped.

  6. 6

    Clean the valve passages, exhaust pipe connection and engine passage of carbon deposits using a scratch awl.

  7. 7

    Remove any gasket material from the valve and engine mating surfaces using a plastic scraper to avoid damage to the surfaces.

  8. 8

    Set the EGR valve in place along with a new gasket.

  9. 9

    Start the two valve-mounting bolts and pipe nut by hand to avoid damage to the threads.

  10. 10

    Tighten the pipe nut using the wrench.

  11. 11

    Tighten the two valve mounting bolts using the ratchet, ratchet extension and socket.

  12. 12

    Repeat the tests from the first section above. If the valve still does not respond, replace it.

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