GM Service Manual Online
For 1990-2009 cars only

Checks

Action

Notice: It is important to correctly identify the source of an oil leak. A power steering fluid leak or spillage can travel across the valley area of the engine and run out the weep hole, which is located at the back of the block. Failure to correctly identify the source of an oil leak can lead to the incorrect or unnecessary replacement of components.

You can repair most fluid leaks by first visually locating the leak, repairing or replacing the component, or by resealing the gasket surface. Once the leak is identified, determine the cause of the leak. Repair the cause of the leak as well as the leak itself.

Locating and identifying the leak

To determine if the leaking fluid is engine oil, transmission fluid, power steering fluid, brake fluid, or some other fluid, use the visual inspection method.

Visual Inspection Method

  1. Bring the vehicle to normal operating temperature.
  2. Park the vehicle over a large sheet of paper, or other clean surface.
  3. Wait several minutes, then check for drippings.
  4. Identify the type of fluid, and the approximate location of the leak.
  5. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
  6. Check for leaks at sealing surfaces, fittings, or from cracked or damaged components.
  7. If you cannot locate the leak, do the following:
  8. 7.1. Completely clean the entire engine and surrounding components.
    7.2. Operate the vehicle for several miles at normal operation temperature and at varying speeds.
    7.3. Park the vehicle over a large sheet of paper, or other clean surface.
    7.4. Wait several minutes, then check for drippings.
    7.5. Identify the type of fluid, and the approximate location of the leak.
    7.6. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
    7.7. See possible causes for leaks.
  9. If you still cannot locate the leak, use the powder method or the black light and dye method.

Powder Method

  1. Completely clean the entire engine and surrounding components.
  2. Apply an aerosol-type powder (baby powder, foot powder, etc.) to the suspected area.
  3. Operate the vehicle for several miles at normal operation temperature and at varying speeds.
  4. Identify the type of fluid, and the approximate location of the leak, from the discolorations in the powder surface.
  5. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
  6. See possible causes for leaks.

Black Light and Dye Method

  1. A dye and light kit is available for finding leaks. Use the J 28428-E High-Intensity Black Light Kit or equivalent. Refer to the manufacturer's instructions when using the tool.
  2. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
  3. See possible causes for leaks.

Possible Causes for Leaks

Check for the following conditions:

    • Higher than recommended fluid levels
    • Higher than recommended fluid pressures
    • Plugged or malfunctioning fluid filters or pressure bypass valves
    • Plugged or malfunctioning engine ventilation system
    • Improperly tightened or damaged fasteners
    • Cracked or porous components
    • Improper sealants or gaskets where required
    • Improper sealant or gasket installation
    • Damaged or worn gaskets or seals
    • Damaged or worn sealing surfaces

Checks

Action

Caution: It is important to correctly identify the source of an oil leak. A power steering fluid leak or spillage can travel across the valley area of the engine and run out the weep hole, which is located at the back of the block. Failure to correctly identify the source of an oil leak can lead to the incorrect or unnecessary replacement of components.

You can repair most fluid leaks by first visually locating the leak, repairing or replacing the component, or by resealing the gasket surface. Once the leak is identified, determine the cause of the leak. Repair the cause of the leak as well as the leak itself.

Locating and identifying the leak

To determine if the leaking fluid is engine oil, transmission fluid, power steering fluid, brake fluid, or some other fluid, use the visual inspection method.

Visual Inspection Method

  1. Bring the vehicle to normal operating temperature.
  2. Park the vehicle over a large sheet of paper, or other clean surface.
  3. Wait several minutes, then check for drippings.
  4. Identify the type of fluid, and the approximate location of the leak.
  5. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
  6. Check for leaks at sealing surfaces, fittings, or from cracked or damaged components.
  7. If you cannot locate the leak, do the following:
  8. 7.1. Completely clean the entire engine and surrounding components.
    7.2. Operate the vehicle for several miles at normal operation temperature and at varying speeds.
    7.3. Park the vehicle over a large sheet of paper, or other clean surface.
    7.4. Wait several minutes, then check for drippings.
    7.5. Identify the type of fluid, and the approximate location of the leak.
    7.6. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
    7.7. See possible causes for leaks.
  9. If you still cannot locate the leak, use the powder method or the black light and dye method.

Powder Method

  1. Completely clean the entire engine and surrounding components.
  2. Apply an aerosol-type powder (baby powder, foot powder, etc.) to the suspected area.
  3. Operate the vehicle for several miles at normal operation temperature and at varying speeds.
  4. Identify the type of fluid, and the approximate location of the leak, from the discolorations in the powder surface.
  5. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
  6. See possible causes for leaks.

Black Light and Dye Method

  1. A dye and light kit is available for finding leaks. Use the J-28428-E High-Intensity Black Light Kit or equivalent. Refer to the manufacturer's instructions when using the tool.
  2. Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
  3. See possible causes for leaks.

Possible Causes for Leaks

Check for the following conditions:

    • Higher than recommended fluid levels
    • Higher than recommended fluid pressures
    • Plugged or malfunctioning fluid filters or pressure bypass valves
    • Plugged or malfunctioning engine ventilation system
    • Improperly tightened or damaged fasteners
    • Cracked or porous components
    • Improper sealants or gaskets where required
    • Improper sealant or gasket installation
    • Damaged or worn gaskets or seals
    • Damaged or worn sealing surfaces