Transmission Fluid Cooler Flushing and Flow Test J 35944-A

Tools Required

1. After the repaired or replacement transmission is installed in the vehicle, do not reconnect the oil cooler pipes.
2. Remove the fill cap on the J 35944-A Transmission Oil Cooler and Line Flusher and fill the can with 0.6 L (20-21 oz.) of J 35944-22 Cooler Flushing Fluid. Do not overfill.
3. Install the fill cap on the J 35944-A and pressurize the flusher can, using a shop air supply regulated at 550-700 kPa (80-100 psi).
4. Connect the J 35944-A discharge hose to the oil cooler return pipe.
5. Clip the discharge hose onto the oil drain container.
6. Attach the J 35944-A to the undercarriage of the vehicle with the hook provided and connect the hose from the J 35944-A to the other (feed) oil cooler pipe.
7. With the water valve on the J 35944-A in the OFF position, connect the water hose from the water supply to the J 35944-A .
8. Turn ON the water supply at the faucet.

1. Turn the water valve on the J 35944-A to the ON position and allow the water to flow through the oil cooler pipes for 10 seconds to remove any remaining transmission fluid. If the water does not flow through the cooler and pipes, the cause of the blockage must be diagnosed and the plugged component must be repaired or replaced. Continue with the cooler flushing and flow check procedure once the blockage is corrected.
2. Turn the water supply on the J 35944-A to the OFF position and clip the discharge hose onto the five gallon pail with a lid.
3. Turn the water valve on the J 35944-A to the ON position and depress the trigger to mix cooler flushing solution into the water flow. Use the clip provided on the handle to hold the trigger down. The discharge will foam vigorously when the solution is introduced into the water stream.
4. Flush the oil cooler and pipes with water and solution for two minutes. During this flush, attach the air supply to the air valve located on the J 35944-A for 3 to 5 seconds at the end of every 15 to 20 second interval to create a surge action.
5. Release the trigger and turn the water valve on the J 35944-A to the off position.

1. Disconnect both hoses from the oil cooler pipes and then connect them to the opposite oil cooler pipe. This will allow the oil cooler and pipes to be back flushed.
2. Repeat steps 3 and 4 on the Initial Flush Procedure.
3. Release the trigger on the J 35944-A and allow water only to rinse the oil cooler and pipes for one minute.
4. Turn OFF the water supply at the faucet.
5. Attach the air supply to the valve on the J 35944-A and blow out the water from the oil cooler and pipes. Continue until no water comes out of the discharge hose.

1. Disconnect both hoses from the oil cooler pipes. Connect the oil cooler feed pipe to the transmission and the return pipe to the discharge hose. Clip the discharge hose onto the empty oil drain container.
2. Confirm the transmission is filled with automatic transmission fluid. Refer to Transmission General Specifications for the correct automatic transmission fluid capacity.
3. Start the engine with the transmission in PARK range and run for 30 seconds. A minimum of 1.9 L (2 quarts) must be discharged during this 30 second run time.

•	If fluid flow is greater than 1.9 L (2 quarts) in 30 seconds, go to step 7.

•	If fluid flow is less than 1.9 L (2 quarts) in 30 seconds, perform the following diagnosis:

4. Disconnect the oil cooler feed line at the radiator.
5. Connect the discharge hose to the cooler feed line. Clip the discharge hose onto the empty oil drain container.
6. Start the engine with the transmission in PARK and run for 30 seconds. A minimum of 1.9 L (2 quarts) must discharge during the 30 second run time. Do the following according to flow rate:

•	Insufficient feed flow: Inspect the transmission.

•	Sufficient feed flow: Inspect the cooler return pipe and the cooler.

7. Remove the discharge hose, reconnect the cooler feed and return pipes to the transmission and refill the unit to the proper fluid level Refer to Transmission General Specifications for the correct automatic transmission fluid capacity.

Transmission Fluid Cooler Flushing and Flow Test J 45096

GM studies indicate that plugged or restricted transmission oil coolers and pipes cause insufficient transmission lubrication and elevated operating temperatures which can lead to premature transmission failure. Many repeat repair cases could have been prevented by following published procedures for transmission oil cooler flushing and flow checking. This procedure includes flow checking and flushing the auxiliary transmission oil cooler, if equipped.

Important: Use the J 45096 or equivalent to flush and flow test the transmission oil cooler and the oil cooler pipes after the transaxle is removed for repairs.

Only GM Goodwrench DEXRON®III automatic transmission fluid should be used when doing a repair on a GM transmission.

Time allowance for performing the cooler flow checking and flushing procedure has been included in the appropriate labor time guide operations since the 1987 model year. The service procedure steps for oil cooler flushing and flow testing are as follows:

1. Machine Set-up
2. Determine Minimum Flow Rate
3. Back Flush
4. Forward Flush
5. Flow Test
6. Code Recording Procedure
7. Clean-up

Tools Required

1. Verify that the main power switch (1) is in the OFF position.
2. Place the main function switch (2) in the IDLE position.



3. Connect J 45096 to the vehicle 12-volt DC power source by connecting the red battery clip to the positive (+) battery post on the vehicle and connect the negative (-) lead to a known good chassis ground.
4. Turn the main power switch to the ON position.




Notice: Do not overfill the supply vessel. Damage to the unit may result. To verify the fluid level, view the LCD screen display while filling the unit, to ensure the fluid level does not exceed 30 L (32 qt).

5. Fill the supply tank with Dexron®III/Mercon®, or equivalent, through the fill port.
6. Install and tighten the fill cap.



7. Connect a shop air supply hose to the quick-disconnect on the rear panel marked SUPPLY AIR.

1. From the machine display, identify the temperature of the automatic transmission fluid that is stored in the supply vessel of J 45096 .



2. Determine whether the transmission oil cooler is steel or aluminum by using a magnet (1) at the cooler flange (2) at the radiator.
3. Refer to the table below. Using the temperature from step 1, locate on either the Steel MINIMUM Flow Rate table or the Aluminum MINIMUM Flow Rate table the minimum flow rate in gallons per minutes (GPM). Record the minimum flow rate in GPMs and the supply fluid temperature for further reference.

Example:

•	Fluid temperature: 24°C (75°F)

•	Cooler type: Steel

The MINIMUM flow rate for this example would be 0.8 GPM.

4. Inspect transmission oil cooler lines for damage or kinks that could cause restricted oil flow. Repair as needed and refer to the appropriate GM service manual procedures.

1. Connect the J 45096 adapters (1) to the vehicle's transmission oil cooler supply and return lines at the transmission, may require J 35944-200 .



2. Connect the black supply hose (1) to the return line, top connector of the transmission, and the clear waste hose (2) to the feed line, bottom connector of the transmission, to the vehicle cooler lines. This is the reverse flow-backflush direction.



3. Turn the main function switch to the FLUSH position. Allow the machine to operate for 30 seconds.



4. Turn the main function switch to the IDLE position and allow the supply vessel pressure to dissipate.

1. Disconnect the supply and waste hoses from the vehicle cooler lines. Reverse the supply and waste hoses to provide a normal flow direction.



2. Turn the main function switch to the FLUSH position and allow the machine to operate for 30 seconds.

Important: If the flow rate is less than 0.5 gpm, the LCD displays an error message. Refer to the Troubleshooting section of the operation manual.

1. Turn the main function switch to the FLOW position and allow the oil to flow for 15 seconds. Observe and note the flow rate. This is the TESTED flow rate.
2. Compare the TESTED flow rate to the MINIMUM flow rate information previously recorded.

•	If the TESTED flow rate is equal to or greater than the MINIMUM flow rate recorded, the oil cooling system is functioning properly. Perform Code Recording Procedure.

•	If the TESTED flow rate is less than the MINIMUM flow rate previously recorded, repeat the back flush and forward flush procedures.

3. If the TESTED flow rate is less than the MINIMUM flow rate after the second test, perform the Code Recording Procedure.

3.1.	Replace the transmission oil cooler.

3.2.	Connect the supply and waste hoses to the cooler lines in the normal flow direction. Perform the Flow Test.

3.3.	Perform the Code Recording Procedure.

1. Turn the main function switch to the CODE position.

Important: 

•	If power is interrupted prior to the recording of the 7-character code, the code will be lost and the flow rate test will need to be repeated.

•	The flow test must run for a minimum of 8-10 seconds and be above 0.5 gpm for a code to be generated.

2. Record TESTED flow rate, temperature, cycle and seven-character flow code information on the repair order.

1. Turn the main function switch to the IDLE position and allow the supply vessel pressure to dissipate.
2. Turn the main power switch to the OFF position.

Important: A small amount of water may drain from the bottom of the unit when the air supply is disconnected. This is a normal operation of the built-in water separator.

3. Disconnect the supply and waste hoses and the 12-volt power source from the vehicle.



4. Disconnect the air supply hose from J 45096 .
5. Dispose of the waste ATF in accordance with all applicable federal, state, and local requirements.