Transmission Fluid Cooler Flushing and Flow Test
Transmission Fluid Cooler Flushing and Flow Test
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.
Note:
Use the DT 45096 - flow test tool or equivalent to flush and flow test the transmission oil cooler and the oil cooler pipes after the transmission is removed for repairs.
Only GM transmission fluid should be used when doing a repair on a GM transmission. Refer to Adhesives, Fluids, Lubricants, and Sealers Adhesives, Fluids, Lubricants, and Sealers.
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:
Cooler Flow Check and Flushing Steps
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
Special Tools
* DT 35944-200A - Cooler Flushing Adapter
* DT 45096 - Transmission Oil Cooling System Flush and Flow Test Tool
* DT 45096-21 - Cooler Flushing Adapter
* Shop air supply with water/oil filters, regulator and pressure gauge-minimum 90 psi
* Eye protection
* Rubber gloves
Machine Set-up
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 DT 45096 - flow test tool 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.
Caution:
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 transmission fluid through the fill port. Refer to Adhesives, Fluids, Lubricants, and Sealers Adhesives, Fluids, Lubricants, and Sealers.
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.
Determine Minimum Flow Rate
The minimum flow rate is 0.5 gpm regardless of fluid temperature.
Back Flush Procedure
1. Connect the DT 45096-21 - adapter (3) and DT 35944-200A - adapter (2) to the vehicle transmission oil cooler supply and return lines (1) at the transmission.
2. Connect the clear waste hose (3) to DT 45096-21 - adapter (1) and DT 35944-200A - adapter (2) connected to the feed line.
3. Connect the black supply hose (3) to DT 45096-21 - adapter (2) and DT 35944-200A - adapter (1) connected to the return line. The clear waste hose and black supply hose are now connected in the reverse flow backflush direction.
4. Turn the main function switch to the FLUSH position. Allow the machine to operate for 30 seconds.
5. Turn the main function switch to the IDLE position and allow the supply vessel pressure to dissipate.
Forward Flush
1. Disconnect the clear waste hose from the DT 45096-21 - adapter at the feed line.
2. Disconnect the black supply hose from the DT 45096-21 - adapter at the return line.
3. Reverse the supply and waste hoses to provide a normal flow direction. Connect the clear waste hose (3) to DT 45096-21 - adapter (2) and DT 35944-200A - adapter (1) connected to the return line.
4. Connect the black supply hose (3) to DT 45096-21 - adapter (1) and DT 35944-200A - adapter (2) connected to the feed line. The clear waste hose and black supply hose are now connected in the normal flow direction.
5. Turn the main function switch to the FLUSH position and allow the machine to operate for 30 seconds.
Flow Test
Note:
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 of 0.5 gpm.
* If the TESTED flow rate is equal to or greater than the MINIMUM flow rate, the oil cooling system is functioning properly. Perform Code Recording Procedure.
* If the TESTED flow rate is less than the MINIMUM flow rate, 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.
1. Replace the transmission oil cooler.
2. Connect the supply and waste hoses to the cooler lines in the normal flow direction. Perform the Flow Test.
3. Perform the Code Recording Procedure.
Code Recording Procedure
1. Turn the main function switch to the CODE position.
Note:
* 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.
Clean-Up
1. Turn the main function switch (2) to the IDLE position and allow the supply vessel pressure to dissipate.
2. Turn the main power switch (1) to the OFF position.
Note:
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 DT 45096 - flow test tool.
5. Dispose of the waste oil in accordance with all applicable federal, state, and local requirements.