GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1996 🢒 Cavalier 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 3T40 🢒 Transmission Component Fluid Leak Diagnosis

Methods for Locating Leaks

You can generally locate and repair the cause of most external leaks with the transmission in the vehicle. Use any one of the following methods for locating leaks:

General Method

  1. Verify that the leak is transmission fluid.
  2. Thoroughly clean the suspected leak area.
  3. Operate the vehicle for about 15 miles or until you have reached normal operating temperatures.
  4. Park the vehicle over clean paper or cardboard.
  5. Shut the engine off and look for fluid spots on the paper.
  6. Make necessary repairs.

Powder Method

  1. Thoroughly clean the suspected leak area with a solvent.
  2. Apply an aerosol type powder such as foot powder to the suspected leak area.
  3. Operate the vehicle for about 15 miles or until you have reached normal operating temperatures.
  4. Shut the engine off.
  5. Inspect the suspected leak area and trace the leak path through the powder to find the source.
  6. Make necessary repairs.

Dye and Black Light Method

  1. Follow the manufacturer's recommendation for the amount of dye to be used.
  2. Find the leak with a black light.
  3. Make the necessary repairs.

Repairing the Leak

Once you have found the leak point, you must next determine the source of the leak. A new gasket will not repair the leak if the sealing flange is bent. You must also repair the bent flange. Before you attempt to repair a leak, check the following conditions:

Gaskets

    • The fluid level or pressure is too high
    • Plugged vent or drain-back holes
    • Improperly torqued fasteners or threads that are dirty or damaged
    • Warped flanges or sealing surface
    • Scratches, burrs, or other damage to the sealing surface
    • A damaged or worn gasket
    • Cracking or porosity of the component
    • Improper sealant
    • Porosity

Seals

    • The fluid level or pressure is too high
    • Plugged vent or drain-back holes
    • Scratches, burrs, nicks, or other damage to the seal bore
    • A damaged or worn seal
    • Improper installation
    • Cracks in the component
    • A scratched or nicked shaft surface
    • A loose or worn bearing, which causes excess seal wear

Possible Points of Oil Leaks
    • Oil may leak from the transmission bottom oil pan or side cover for the following reasons:
       - The attaching bolts are not torqued correctly.
       - The gasket is damaged or improperly installed.
       - The oil pan or the mounting face is not flat.
    • Oil may leak from the case for the following reasons:
       - The multi-lip seal on the filler tube is damaged or missing.
       - The filler tube bracket is misaligned.
       - The speed sensor seal is damaged.
       - The manual shaft seal is damaged.
       - The connector fittings on the oil cooler are loose or damaged.
       - The propeller shaft oil seal is worn or damaged.
       - The plug from the line pressure pipe is loose.
       - The casting is porous.
    • Oil may leak from the converter end for the following reasons:
       - The converter seal is damaged.
   • The seal lip is cut (check the converter hub for damage).
   • The bushing has been moved forward and is damaged.
   • A garter spring is missing from the seal.
       - The converter is leaking from a weld area.
       - A casting is porous in the case or the pump.
    • Fluid may come out from the vent pipe or the fill tube under the following conditions:
       - Overfilled
       - If the fluid appears milky, water or coolant may be in the fluid.
       - The case is porous.
       - The fluid level indicator registers incorrectly.
       - A vent is plugged.
       - The drain back holes are plugged.
       - The oil pump is misaligned to the case gasket, if equipped.

Case Porosity Repair Procedure
  1. Thoroughly clean the area to be repaired with a cleaning solvent. Air dry.

    2. Caution: Epoxy adhesive may cause skin irritations and eye damage. Read and follow all information on the container label as provided by the manufacturer.

  2. Using instructions from the manufacturer, mix a sufficient amount of epoxy, GM P/N 1052533 or equivalent, to make the repair.
  3. While the transmission case is still hot, apply the epoxy. You can use a clean, dry soldering acid brush to clean the area and also to apply the epoxy cement. Make certain that the area to be repaired is fully covered.
  4. Allow the epoxy cement to cure for three hours before starting the engine.
  5. Repeat the fluid leak diagnosis procedures.