GM Service Manual Online
For 1990-2009 cars only

Oil Cooler Flushing Procedure

Tool Required

J 35944-A Oil Cooler and Line Flusher

Caution: Air supply must be equipped with a water and oil filter. This air supply must not exceed 825 kPa (120 psi). Excess air pressure may rupture the flushing cooler, causing personal injury.

Important: After the repaired or replacement transmission/transaxle is installed in the vehicle, do not reconnect the oil cooler pipes, perform the following procedure.

  1. Remove the fill cap on the J 35944-A .
  2. Use 0.6 liters (20 ounces) of flushing solution to fill the J 35944-A . Follow the manufacturer's suggested procedures for the handling of the solution. Do NOT overfill.
  3. Replace the cap on the J 35944-A .
  4. Pressurize the J 35944-A to 550-700 kPa (80-100 psi).
  5. Connect a discharge hose to the transaxle end of the oil cooler pipe that feeds the BOTTOM fitting of the oil cooler and clip the discharge hose to the oil drain container.
  6. Connect the feed hose from the J 35944-A to the remaining oil cooler pipe.
  7. Ensure the J 35944-A water valve is in the OFF position.
  8. Connect the water supply to the J 35944-A .
  9. Turn the water supply on.
  10. Caution: If water does not flow through the cooler, do not continue with the flushing procedure. The cooling system may be plugged and excess pressure may rupture the cooler, causing personal injury. Replace the cooler pipe or the cooler if necessary.

  11. Turn the water valve to the ON position for about 10 seconds to flush the transaxle fluid.
  12. Close the water valve.
  13. Clip the discharge hose to the 5 gallon pail.
  14. Cover the pail with a shop towel to prevent splashing.
  15. Turn the water valve to the ON position.
  16. Depress the trigger to mix the flushing solution into the water flow.
  17. Use the bale clip provided to hold the trigger down.
  18. Use water and the solution to flush the cooler for two minutes.
  19. Attach the air supply to the air valve located on the J 35944-A for three to five seconds every 15-20 seconds during the flush. This creates a surging action to ensure complete cleaning.
  20. Release the trigger.
  21. Turn the water valve off.
  22. Disconnect both hoses from the oil cooler pipes.
  23. Reconnect the hoses to the pipes opposite the initial flush to perform a backflush.
  24. Repeat step 15 through step 19.
  25. Release the trigger.
  26. Allow water to rinse for one minute.
  27. Turn the water valve off.
  28. Turn the water supply off.
  29. Attach the air supply to the air valve.
  30. Dry the system out with air until no moisture is seen leaving the discharge hose.
  31. Connect the cooler feed pipe to the transaxle.
  32. Reconnect the discharge hose to the cooler return pipe.
  33. Clip the discharge hose to the oil drain container.
  34. Start the engine after filling the transaxle with fluid.
  35. Run the engine for 30 seconds. This removes any residual moisture from the oil cooler. A minimum of 1.9 liter (2 quarts) of fluid should flow during the 30 second period.
  36. Perform the following steps if the fluid flow is insufficient:
  37. 35.1. Disconnect the feed line at the cooler.
    35.2. Observe the flow while the engine is running to check the fluid flow from the transaxle.
    35.3. Inspect the transaxle for a possible cause.
    35.4. Inspect the cooler pipes if flow from transaxle is insufficient.
    35.5. Inspect the fittings if flow from transaxle is insufficient.
    35.6. Repeat the cooler flushing procedure.
    35.7. Replace the cooler if the flow through the cooler is still insufficient. Refer to Engine Cooling.
  38. Remove the discharge hose.
  39. Connect the cooler pipe.
  40. Adjust the fluid level. Refer to. Approximate Fluid Capacities in Maintenance and Lubrication and Fluid and Lubricant Recommendations in Maintenance and Lubrication.
  41. Inspect for proper completion of the repairs.
  42. Inspect for fluid leaks.