This procedure covers the replacement of the transmission oil cooler, which circulates ATF to prevent transmission overheating. This is a common repair for leaking or damaged coolers.

Warnings

Tools required

Parts

• Transmission oil cooler × 1 — Use OEM specification
• Transmission cooler line O-rings × 4 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification

Fluids

• Motorcraft MERCON LV ATF — 11 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine and transmission to cool if recently driven
3. Raise front of vehicle and support securely on jack stands
4. Remove engine splash shield and transmission skid plate if equipped
5. Place large drain pan under transmission pan

Procedure

1. 1

   Drain transmission fluid
   Remove the transmission drain plug and allow fluid to drain completely into drain pan. This will take several minutes. Once drained, reinstall drain plug with new crush washer.
   Torque spec

   Transmission Drain Plug30 Nm (22 lb-ft)
2. 2

   Locate transmission oil cooler
   The transmission oil cooler is mounted to the front of the transmission case, below the transmission pan. Identify the two cooler lines connecting to the cooler from the radiator. Clean the area around the cooler and line connections to prevent contamination.
   ℹ️On 4WD models, the transfer case may obstruct access. You may need to work from multiple angles.
3. 3

   Disconnect transmission cooler lines
   Using a line wrench, carefully loosen and disconnect both transmission cooler lines from the oil cooler. Expect residual fluid to drain from the lines. Cap or plug the lines immediately to prevent contamination. Note the orientation and position of each line for reassembly.
   ⚠Use line wrenches to prevent rounding off the fittings. Standard wrenches may damage the cooler line nuts.
4. 4

   Remove oil cooler mounting bolts
   Remove the mounting bolts securing the transmission oil cooler to the transmission case. There are typically 2-3 bolts depending on cooler design. Support the cooler as you remove the final bolt to prevent it from falling.
   Torque spec

   Mounting Bolts70 Nm (52 lb-ft)
5. 5

   Remove transmission oil cooler
   Carefully pull the oil cooler away from the transmission case. Residual fluid will drain from the cooler and internal passages. Remove and discard the old O-rings from the cooler line ports on both the cooler and transmission case.
   ℹ️Inspect the cooler mounting surface on the transmission case for damage or debris.
6. 6

   Prepare new oil cooler
   Install new O-rings on the cooler line ports of the new oil cooler. Lightly lubricate the O-rings with clean MERCON LV ATF to aid installation and prevent damage. Compare the new cooler to the old unit to verify correct replacement part.
   ⚠Do not use petroleum-based lubricants on O-rings as they will damage the seals.
7. 7

   Install new oil cooler
   Position the new oil cooler to the transmission case, aligning the mounting holes. Install the mounting bolts and tighten in a cross pattern to specified torque. Ensure the cooler is seated flush against the transmission case.
   Torque spec

   Mounting Bolts70 Nm (52 lb-ft)
8. 8

   Reconnect transmission cooler lines
   Install new O-rings on the transmission cooler line fittings if not already replaced. Reconnect both cooler lines to the new oil cooler, ensuring they are properly aligned. Hand-tighten the fittings first, then use a line wrench to snug them. Do not overtighten.
   ⚠Overtightening cooler line fittings can crack the cooler housing or strip the threads.
9. 9

   Refill transmission
   Using a transmission fluid funnel inserted into the dipstick tube, add approximately 5-6 quarts of MERCON LV ATF initially. Start the engine and allow it to idle. With the engine running and transmission in Park, check fluid level and add fluid as needed to reach the cold range on the dipstick.
   ℹ️Do not overfill. The transmission must be cycled through gears and warmed to operating temperature for accurate level check.
10. 10

    Check for leaks
    With the engine running at idle, inspect all cooler connections and the cooler mounting area for signs of leakage. Wipe connections clean and observe for several minutes. If leaks are present, shut off engine and address before proceeding.
    ⚠Never check for leaks with your hands. Use a clean towel or shop rag to detect fluid.
11. 11

    Cycle transmission and recheck fluid level
    With engine at operating temperature and foot on brake, shift through all gear ranges (P-R-N-D and manual gates if equipped), pausing 2-3 seconds in each position. Return to Park and recheck fluid level. Add fluid as needed to bring level to the hot range on dipstick. Total capacity should be approximately 11 quarts.
    ℹ️Proper fluid level is critical. Too low causes shifting issues and damage; too high causes foaming and erratic operation.

Reassembly

1. Reinstall transmission skid plate if equipped, torque to specification
2. Reinstall engine splash shield
3. Lower vehicle from jack stands
4. Dispose of used ATF properly at a recycling facility
5. Road test vehicle to verify proper transmission operation and no leaks

Verification

• Verify no transmission fluid leaks at cooler or line connections after road test
• Confirm transmission shifts smoothly through all gears without slipping or delay
• Verify transmission fluid level is in the hot range on dipstick with engine at operating temperature
• Check transmission temperature does not exceed normal operating range (180-200°F)
• Inspect ground under vehicle after overnight parking to confirm no fluid leaks

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