Replace the transmission oil cooler, which cools automatic transmission fluid and is integrated into the radiator assembly on this vehicle.

Warnings

Tools required

Parts

• Transmission oil cooler assembly × 1 — Use OEM specification
• Transmission cooler line O-rings × 2 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification

Fluids

• Toyota WS ATF — 4 qt

Preparation

1. Ensure engine and transmission are completely cool to the touch
2. Park vehicle on level ground and engage parking brake
3. Place wheel chocks behind rear wheels
4. Disconnect negative battery terminal
5. Remove engine splash shield/under cover using 10mm socket
6. Place drain pan under transmission drain plug

Procedure

1. 1

   Drain transmission fluid
   Remove the transmission drain plug located on the bottom of the transmission pan. Allow fluid to drain completely into drain pan. Once drained, reinstall drain plug with new crush washer.
   Torque spec

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

   Access transmission cooler lines
   Remove the front grille or access panel to expose the radiator and transmission cooler lines. On most 2014-2019 Corollas, this requires removing plastic clips and screws securing the upper grille assembly. Use trim removal tools to avoid breaking clips.
   ℹ️Take photos of clip locations before removal for easier reassembly.
3. 3

   Disconnect upper transmission cooler line
   Locate the upper transmission cooler line connection at the radiator. Clean the area around the connection. Use a line disconnect tool or flare nut wrench to disconnect the line from the radiator-mounted cooler. Have a drain pan ready as residual fluid will drain. Cap the open line immediately to prevent contamination.
   ⚠Do not use regular wrenches on cooler line fittings as they will round off the soft metal nuts.
4. 4

   Disconnect lower transmission cooler line
   Repeat the disconnection process for the lower transmission cooler line. Position drain pan to catch remaining fluid. Cap both the line and the cooler port to prevent dirt entry.
   ⚠Inspect disconnected lines for damage, cracks, or excessive wear. Replace if compromised.
5. 5

   Remove old transmission oil cooler
   If the cooler is a separate component mounted to the radiator, remove mounting bolts or brackets securing it. If integrated into the radiator assembly, the entire radiator will need replacement. For bolt-on coolers, remove the fasteners and carefully extract the cooler.
   Torque spec

   Mounting Bolts26 Nm (19 lb-ft)
6. 6

   Prepare new transmission oil cooler
   Unpack the new transmission oil cooler and verify all mounting points match the original. Install new O-rings on the cooler line ports, lubricating them lightly with clean ATF. Ensure all sealing surfaces are clean and free of debris.
   ℹ️Do not reuse old O-rings as they will leak under pressure and temperature cycling.
7. 7

   Install new transmission oil cooler
   Position the new cooler in place and secure with mounting bolts. Ensure the cooler is properly aligned and all brackets are seated correctly before tightening fasteners.
   Torque spec

   Mounting Bolts26 Nm (19 lb-ft)
8. 8

   Reconnect transmission cooler lines
   Remove caps from cooler ports and transmission lines. Connect the upper and lower cooler lines to the new cooler, ensuring connections are straight and not cross-threaded. Hand-tighten first, then use flare nut wrench to snug. Do not overtighten as this can damage the soft metal fittings.
   ⚠Ensure lines are routed correctly and not kinked, twisted, or touching hot engine components.
9. 9

   Refill transmission fluid
   Locate the transmission fill plug or dipstick tube. Using a funnel, add approximately 4 quarts of Toyota WS ATF. Start the engine and allow it to reach normal operating temperature while cycling through all gear positions (P-R-N-D-L) pausing 2-3 seconds in each position. Check fluid level according to transmission dipstick markings or level plug procedure.
   ⚠Add fluid in small increments and check level frequently. Overfilling can damage the transmission.
10. 10

    Check for leaks
    With engine running and transmission at operating temperature, carefully inspect all cooler line connections for leaks. Look for fluid seepage or drips. Also check the transmission drain plug. Tighten connections slightly if minor seepage is observed, but do not overtighten.

Reassembly

1. Reinstall front grille or access panel with all clips and fasteners
2. Reinstall engine splash shield/under cover
3. Reconnect negative battery terminal
4. Remove wheel chocks
5. Dispose of used ATF according to local regulations

Verification

• Start engine and verify no leaks at transmission cooler connections after 5 minutes of idling
• Test drive vehicle through all gears, verifying smooth shifting operation
• Re-check transmission fluid level when hot and adjust if necessary
• Inspect under vehicle for any fluid drips after test drive
• Monitor transmission temperature gauge (if equipped) for normal operating range during first few drives

More procedures for this vehicle