O-Ring Stops Ford Fluid Leak

By Chris Burton and Jeff Webster

On certain Ford, Mercury and Lincoln vehicles, you may notice transmission fluid leaking between the radiator transmission oil cooler and the transmission oil cooler fitting (NOT the cooler line into the fitting). This may result in a residue of transmission fluid on the radiator tank around the transmission oil cooler fitting. The leak may be caused by insufficient thread sealer on the transmission oil cooler fitting. Note: This technical service bulletin (TSB) does not apply to transmission fluid leakage at the transmission line to transmission oil cooler fitting.

Applicable Vehicles
1997-2000 Ford Mustang, Expedition, Explorer, F-150, F-250 LD
1998-2000 Ford Ranger, Lincoln Navigator, Mercury Mountaineer
1999-2000 Ford F-Series Super Duty

Parts Information
P/N W705181-S (O-Ring)

Repair Procedure
1. Verify that transmission fluid is leaking between the transmission oil cooler and the transmission oil cooler fitting, NOT the transmission cooler line fitting into the transmission oil cooler fitting (Figure 1).

2. Remove the radiator from the vehicle. Place the radiator on a flat surface so that the transmission oil cooler fittings are facing upward (Figure 2).

3. Clean the area around the transmission oil cooler fitting. This will ensure that contaminants do not enter the transmission oil cooler when the transmission oil cooler fittings are removed. 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.

4. Remove the upper transmission oil cooler fitting. Note: Remove only one (1) transmission oil cooler fitting at a time, otherwise the cooler may drop into the radiator.

5. Once the fitting is removed from the transmission oil cooler, verify that there is a gasket between the transmission oil cooler and the inside of the radiator tank. If there is no gasket, replace the radiator. If the gasket is in place, continue to Step 6.

6. Inspect the transmission oil cooler fitting threads for damage. If the threads are damaged, replace the radiator. If the threads show no sign of damage, continue to Step 7.

7. Install O-ring W705181-S on the transmission oil cooler fitting (Figures 2 and 3). Caution: Thread sealant or tape should never be used on the threads of the transmission oil cooler fitting. The use of such materials will create a leak path.

8. Making sure that the gasket between the transmission oil cooler and the inside of the radiator tank is still in place, reinstall the transmission oil cooler fitting. Torque the fitting to 28-33 lb-ft (38-45 N.m). Note: Do not use air tools to torque the transmission oil cooler fitting. Use a hand-operated torque wrench only.

9. Repeat Steps 2-8 for the other transmission oil cooler fitting. This fitting should also have the O-ring replaced even if it is not leaking.

10. Make sure that no radiator coolant has entered the transmission oil cooler. Reinstall the radiator in the vehicle, fill with coolant and test run engine to warm condition.

11. Verify that both the transmission and the engine cooling system have the proper fluid levels, and that thermostat has cycled open at least once during engine test run.

CHRIS BURTON is a senior quality engineer with ALLDATA. His experience includes six years as a U.S. Navy main propulsion technician, and more than 20 years as a driveability, body/paint and suspension technician; body shop manager; service and parts manager. He is a double-certified ASE Master Tech in both automotive and body and paint.

JEFF WEBSTER is a technical writer with ALLDATA. He has more than 20 years experience as a writer/editor.

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