Leakage Inspection

NOTE: Do not try to stop the transmission fluid leak by increasing the torque beyond specifications. This may cause damage to the case threads.

Check transmission fluid cooler tubes and fittings between the transmission and the transmission fluid cooler for wear or damage. When transmission fluid is found leaking between the case and the transmission fluid cooler tube fitting, check for a missing or damaged seal, then tighten the fitting to specification.
REFER to: Transmission Fluid Cooler Tubes (307-02A Transmission Cooling - Vehicles With: 6-Speed Automatic Transmission - 6F50, Removal and Installation).

If the leak continues, install new transmission fluid cooler tubes and tighten to specification.
REFER to: Transmission Fluid Cooler Tubes (307-02A Transmission Cooling - Vehicles With: 6-Speed Automatic Transmission - 6F50, Removal and Installation).

Check the engine coolant in the radiator. If transmission fluid is present in the engine coolant, the transmission fluid cooler is probably leaking. The transmission fluid cooler can be further checked for leaks by disconnecting the transmission fluid cooler tubes from the transmission fluid cooler and applying no more than 50.0  psi ( 345  kPa) of air pressure to the transmission fluid cooler fitting. Remove the engine coolant reservoir cap to relieve the pressure. If the transmission fluid cooler is leaking and will not hold pressure, install a new transmission fluid cooler.
REFER to: Transmission Fluid Cooler (307-02A Transmission Cooling - Vehicles With: 6-Speed Automatic Transmission - 6F50, Removal and Installation).

Leak Check Test

NOTE: When diagnosing transmission leaks, the source of the leak must be positively identified prior to repair. If the vehicle is driven extensively between adding the fluorescent additive and performing the leak test, the leaking oil can spread and make identifying the location of the leak difficult.

1. Clean off any transmission fluid from the top and bottom of the torque converter housing, the front of the case and rear face of the engine and oil pan. Clean the torque converter area by washing with a nonflammable solvent and blow dry with compressed air.
   

1. Add leak detection dye (-) to the transmission fluid.
   

Use one 1.01 fl oz ( 30  ml) of dye solution for every 4.01  qt ( 3.8  L) of transmission fluid.

1. Start and run the engine until the transmission reaches its normal operating temperature. Raise the vehicle on a hoist and with the engine running, shift to the DRIVE and REVERSE ranges to increase pressure within the transmission. Using a black light, observe the back of the cylinder block and top of the torque converter housing for evidence of fluid leakage. Run the engine until transmission fluid leakage is evident and the probable source of leakage can be determined.
   

1. If the source of the leak is obvious, repair as required. Leaks from the torque converter housing can originate from several locations. The paths which the fluid takes to reach the bottom of the torque converter housing are shown in the illustration. The 5 following steps correspond with the numbers in the illustration.
   
   1. Transmission fluid leaking by the converter hub seal lip will tend to move along the drive hub and onto the back of the torque converter. Except in the case of a total seal failure, transmission fluid leakage by the lip of the seal will be deposited on the inside of the torque converter housing only, near the outside diameter of the housing.
      
   1. Transmission fluid leakage by the outside diameter of the converter impeller hub seal and the case will follow the same path that leaks by the inside diameter of the converter hub seal follow.
      
   1. Transmission fluid leakage from the converter cover weld or the converter-to-flexplate stud weld will appear at outside diameter of torque converter on the back face of the flexplate and in the converter housing only near the flexplate. If a converter-to-flexplate lug, lug weld or converter cover weld leak is suspected, remove the converter and pressure check.
      
   1. Transmission fluid leakage from the bolts inside the converter housing will flow down the back of the torque converter housing. Leakage may be from loose or missing bolts.
      
   1. Engine oil leaks from the rear main oil.
      

1. Remove the torque converter.
   

1. Using a black light, observe the torque converter housing. Inspect for evidence of dye from the pump bolts, pump seal, and torque converter hub seal. Repair as required.
   

1. If the source of the leak is not evident, continue with this procedure to leak test the torque converter.
   

1. Place the torque converter in an arbor press. Support the torque converter on the mounting pads.
   

1. Install the torque converter leak tester (307-421) into the torque converter hub.
   

1. Secure the press. Apply enough force from the press to seal the torque converter leak tester (307-421) into the torque converter hub.
   

1. Connect a compressed air supply to the torque converter leak tester (307-421).
   

1. Inspect for leaks at the converter hub weld and seams with air pressure applied to the valve. A soap bubble solution can be applied around those areas to aid in the diagnosis. If any leaks are present, install a new torque converter.
   

1. Inspect for leaks at the stud or mounting pad and balance weight welds. A soap bubble solution can be applied around those areas to aid in the diagnosis. If any leaks are present, install a new torque converter.
   

1. After leaks are repaired, clean the remaining transmission fluid dye from serviced areas.
   

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