GM Service Manual Online
For 1990-2009 cars only

Transmission Fluid Cooler Flushing and Flow Test Flushing Procedure

Notice: Whenever you remove the transmission for service, you must perform the automatic transmission oil cooler flushing procedure in order to remove the existing fluid which may be contaminated. This will prevent contamination of the new fluid. You must perform the flushing procedure after the installation of the overhauled or replacement transmission.

After filling the transaxle with fluid, start the engine and run for 30 seconds. This will remove any residual moisture from the oil cooler. Disconnect the return line at the transaxle and observe the flow with the engine running. If the fluid flow is insufficient, check the fluid flow by disconnecting the feed line at the cooler. Observe the flow with the engine running.

    • If the flow from the cooler return line at the transaxle is insufficient, inspect the flow rate from the feed line to the cooler. Blockage exists in the transaxle or the cooler.
    • If the flow from the transaxle feed line to the cooler is insufficient, the transaxle is the cause of the fluid flow problem.
    • If the flow from the transaxle feed line to the cooler is insufficient, but flow from the cooler return line to the transaxle is insufficient, inspect the cooler pipes and fittings. Then repeat the cooler flushing procedure. If the flow is still insufficient, replace the cooler.