This procedure covers the removal and replacement of transmission cooler lines on a 2014-2019 Toyota Corolla with 1.8L I4 engine, including fluid drainage and refilling.

Warnings

Tools required

Parts

• Transmission cooler line set × 1 — Use OEM Toyota specification or equivalent
• Transmission drain plug crush washer × 1 — 90430-12031 or equivalent
• Transmission cooler line O-rings × 4 — Typically included with cooler line set

Fluids

• Toyota WS ATF — 3 qt

Preparation

1. Park vehicle on level surface and apply parking brake
2. Place wheel chocks behind rear wheels
3. Verify engine and transmission are cool to the touch
4. Raise front of vehicle using floor jack and support on jack stands at manufacturer-specified lift points
5. Remove driver side front wheel for improved access (optional but recommended)
6. Remove engine splash shield by removing 10mm fasteners and push clips
7. Position drain pan under transmission drain plug area

Procedure

1. 1

   Drain transmission fluid
   Locate the transmission drain plug on the bottom of the transmission pan. Using a 14mm socket, slowly loosen the drain plug. Allow fluid to drain completely into drain pan. Once drained, remove old crush washer from drain plug and install new crush washer. Reinstall drain plug and torque to specification.
   Torque spec

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

   Access transmission cooler lines at radiator
   Locate the two transmission cooler lines at the lower driver side of the radiator. These are metal lines with threaded fittings. Clean the area around both fittings with shop towels to prevent contamination. Position drain pan under the radiator connection points to catch residual fluid.
3. 3

   Disconnect cooler lines from radiator
   Using a flare nut wrench, carefully loosen the upper cooler line fitting at the radiator. Do not use standard wrenches as they may round the fitting. Once loose, unthread by hand and allow residual fluid to drain. Repeat for the lower cooler line. Cap or plug the radiator ports with clean shop towels to prevent contamination.
   ⚠Use only flare nut wrenches on these fittings. Standard wrenches will round off the soft metal fittings.
4. 4

   Disconnect cooler lines from transmission
   Move drain pan under transmission. Locate where cooler lines connect to the transmission case on the driver side. Using flare nut wrench, loosen and remove both line fittings from the transmission. Allow any remaining fluid to drain. Remove the retaining clips or brackets securing the lines to the transmission using 10mm socket if equipped.
5. 5

   Remove old cooler lines
   Trace the routing of the old cooler lines from transmission to radiator. Remove any mounting clips or brackets along the frame rail and subframe using 10mm socket. Carefully extract the lines from the vehicle, noting the exact routing path and orientation for installation of new lines. Take photos if necessary for reference.
6. 6

   Prepare new cooler lines
   Unpack new cooler lines and verify they match the old lines in length and fitting configuration. Install new O-rings on all four line ends if not pre-installed. Lightly coat O-rings with clean Toyota WS ATF to aid installation and prevent damage. Verify all fittings are clean and free of debris.
7. 7

   Route and install new cooler lines
   Route the new cooler lines along the same path as the original lines, ensuring they do not contact exhaust components, sharp edges, or moving parts. Install mounting clips and brackets along the frame rail and subframe, securing with 10mm fasteners. Ensure lines have adequate clearance and are not kinked or twisted.
8. 8

   Connect cooler lines to transmission
   Thread the cooler line fittings into the transmission by hand to ensure proper engagement. Once hand-tight, use flare nut wrench to tighten fittings snugly. Do not over-tighten as this may damage the O-rings or threads. Typical tightness is 15-20 lb-ft but use feel to avoid cross-threading.
   ⚠Start all fittings by hand first. Cross-threading will damage transmission case threads requiring expensive repair.
9. 9

   Connect cooler lines to radiator
   Remove protective plugs or towels from radiator ports. Thread cooler line fittings into radiator by hand until fully seated. Use flare nut wrench to snug fittings. Verify both lines are securely attached and properly oriented without twisting or stress on the lines.
10. 10

    Refill transmission fluid
    Locate the transmission fill plug on the driver side of the transmission case. Remove fill plug using 10mm hex socket. Using a fluid transfer pump, add approximately 3 quarts of Toyota WS ATF through the fill hole. Fluid should reach the bottom of the fill plug hole when level is correct. Reinstall fill plug.
    ℹ️Final fluid level check must be performed with engine running and transmission at operating temperature.
11. 11

    Check for leaks (cold check)
    Inspect all four cooler line connections at the transmission and radiator for signs of leakage. Wipe all connections dry with shop towel, then visually verify no fluid is seeping from fittings. Check the drain plug for leaks as well.

Reassembly

1. Reinstall engine splash shield and secure all fasteners
2. Reinstall driver side front wheel if removed and torque lug nuts to 103 Nm (76 lb-ft) in star pattern
3. Lower vehicle from jack stands to ground
4. Remove wheel chocks

Verification

• Start engine and allow to idle. Verify no warning lights on dashboard.
• With engine running and parking brake applied, shift transmission through all gear positions, pausing 3 seconds in each position.
• Return to Park. With engine at idle, check transmission fluid level using dipstick or fill plug method per owner's manual. Add fluid as needed to reach proper level.
• Perform a careful inspection under the vehicle while engine is running. Check all four cooler line connections and drain plug for any signs of leakage.
• Test drive vehicle for 10-15 minutes, bringing transmission to full operating temperature. Re-check fluid level after test drive.
• Perform final under-vehicle inspection for leaks after test drive. Address any leaks immediately.

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