Transmission Fluid Cooler Leaks at Radiator

Transmission fluid may leak between the radiator transmission fluid cooler and the transmission fluid cooler fitting (not the cooler line into the fitting), which may result in a residue of transmission fluid on the radiator tank around the fluid cooler fitting. Insufficient thread sealer on the transmission fluid cooler fitting may cause this.

1. Clean the area around the transmission fluid cooler fittings.
Fig 1: Cleaning Area Around Transmission Fluid Cooler Fittings
Courtesy of FORD MOTOR CO.
2. Verify that transmission fluid is leaking between the transmission fluid cooler and the transmission fluid cooler fitting (not the transmission fluid cooler line fitting into the transmission fluid cooler fitting).
Fig 2: Locating Transmission Fluid Leak
Courtesy of FORD MOTOR CO.
3. Remove the radiator from the vehicle and place it on a flat surface with the transmission fluid cooler fittings facing upward. For additional information, refer to ENGINE COOLING .
CAUTION: Oil-based solvents and cleaners should not be used when cleaning the radiator. Oil-based solvents and cleaners can damage the radiator end tank seals and cause leaks.
Fig 3: Removing Transmission Fluid Cooler Fittings
Courtesy of FORD MOTOR CO.
4. Clean the area around the transmission fluid cooler fittings so that contaminants do not enter the transmission fluid cooler when the transmission fluid cooler fittings are removed.
NOTE: Remove only one transmission fluid cooler fitting at a time, otherwise the cooler may drop into the radiator.
5. Remove the upper transmission fluid cooler fitting.
6. Once the fitting is removed from the transmission fluid cooler, verify that there is a gasket between the transmission fluid cooler and the inside of the radiator tank.
   • If there is no gasket, install a new radiator.
   • If there is a gasket, proceed to the next step.
7. Inspect the transmission fluid cooler fitting threads for damage.
   • If the threads are damaged, install a new radiator.
   • If the threads show no sign of damage, proceed to the next step.
     Fig 4: Inspecting Transmission Fluid Cooler Fitting Threads

     Courtesy of FORD MOTOR CO.
CAUTION: Thread sealant or tape should never be used on the threads of the transmission fluid cooler fittings. The use of such materials will create a leak path.
Fig 5: Installing A New O-Ring On Transmission Fluid Cooler Fitting
Courtesy of FORD MOTOR CO.
8. Install a new O-ring on the transmission fluid cooler fitting.
NOTE: Do not use air tools to tighten the transmission fluid cooler fitting. Use a hand-operated torque wrench only.
9. Making sure that the gasket between the transmission fluid cooler and the inside of the radiator tank is still in place, install the transmission fluid cooler fitting.
10. Follow the procedure to install a new O-ring on the other transmission fluid cooler fitting.
11. Make sure that no radiator coolant has entered the transmission fluid cooler. Install the radiator in the vehicle.
12. Verify that both the transmission and the engine cooling system are at the correct fluid levels.