Replace or repair transmission cooler lines on a 2016-2024 Hyundai Tucson with 2.5L I4 AWD engine, including fluid drainage and refill.

Warnings

Tools required

Parts

• Transmission cooler lines (supply and return) × 1 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification
• Cooler line O-rings/seals × 1 — Use OEM specification
• Transmission pan gasket (if resealing) × 1 — Use OEM specification

Fluids

• Hyundai SP-IV-M ATF — 10 qt

Preparation

1. Park vehicle on level surface and apply parking brake
2. Place wheel chocks behind rear wheels
3. Allow engine and transmission to cool completely (minimum 2 hours after operation)
4. Raise front of vehicle with floor jack and support securely on jack stands
5. Remove front plastic splash shield/under cover using 17mm socket
6. Position large drain pan under transmission

Procedure

1. 1

   Drain transmission fluid
   Locate transmission drain plug on bottom of transmission pan. Clean area around drain plug with wire brush and brake cleaner. Using 14mm socket, slowly loosen drain plug while keeping pressure on it to prevent dropping. Remove drain plug and crush washer completely, allowing fluid to drain into pan. Wait until flow reduces to slow drip (approximately 10-15 minutes).
   Torque spec

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

   Locate and identify cooler lines
   Identify the two transmission cooler lines running from the transmission to the cooler at the front of the vehicle. The supply line (from transmission to cooler) is typically the upper line, and the return line (from cooler to transmission) is the lower line. Trace lines to identify connection points at transmission housing and at radiator/cooler assembly. Note the routing and any clips or retainers securing lines to body or frame.
3. 3

   Disconnect cooler lines at transmission
   Starting at the transmission end, clean the connection area thoroughly. For quick-connect fittings: press line disconnect tool onto fitting and pull line away from transmission. For threaded fittings: use appropriate flare nut wrench to prevent rounding. Position catch tray under connection as residual fluid will drain. Remove and inspect O-rings or seals for damage. Mark or photograph line positions to ensure correct reinstallation.
   ⚠Do not use standard open-end wrenches on flare fittings as they will round the soft metal. Use only flare nut wrenches.
4. 4

   Disconnect cooler lines at radiator/cooler
   Move to front of vehicle and locate where cooler lines connect to the transmission cooler (integrated into radiator or separate). Clean connection area. Disconnect fittings using same method as transmission end. For integrated coolers, connections are typically on driver's side of radiator. Allow any residual fluid to drain into pan. Remove any retaining clips securing lines to frame or body along the routing path.
5. 5

   Remove old cooler lines
   Carefully remove cooler lines from vehicle, noting exact routing path, clearances from exhaust components, and locations of all mounting clips and brackets. Take photos for reference during installation. Inspect old lines for failure point: check for rust perforation, impact damage, chafing from contact with other components, or deteriorated rubber sections at connections.
6. 6

   Prepare new cooler lines
   Unpack new cooler lines and verify they match old lines in length, fitting type, and bend configuration. Install new O-rings or seals on line ends, lightly lubricating with clean ATF. Verify all connection fittings are clean and free of debris. Compare new lines to photos of old line routing to plan installation path.
7. 7

   Install new cooler lines
   Route new cooler lines along same path as original lines, ensuring adequate clearance from exhaust manifold, catalytic converter, and moving suspension components. Start by connecting lines at radiator/cooler end first. For quick-connect: push firmly until you hear/feel a click. For threaded: hand-thread first, then tighten with flare nut wrench until snug (do not overtighten). Install all mounting clips and retainers in original positions.
8. 8

   Connect cooler lines to transmission
   Connect cooler lines to transmission housing fittings. Ensure lines are correctly identified (supply and return). For quick-connect fittings, push firmly until seated and locked. For threaded fittings, hand-thread to avoid cross-threading, then tighten snugly with flare nut wrench. Verify lines have no kinks, sharp bends, or contact points with hot or moving components. Secure any remaining clips or brackets.
9. 9

   Reinstall drain plug and prepare for refill
   Clean drain plug threads with brake cleaner and wire brush. Install new crush washer on drain plug. Thread drain plug in by hand to verify proper thread engagement. Torque drain plug to specification using torque wrench.
   Torque spec

   Transmission Drain Plug30 Nm (22 lb-ft)
10. 10

    Refill transmission fluid
    Locate transmission dipstick/fill tube near firewall on driver's side. Insert funnel with extension tube. Add approximately 6 quarts of Hyundai SP-IV-M ATF initially. Start engine and allow to idle in Park. Shift through all gear positions (P-R-N-D-L), pausing 3 seconds in each. Return to Park. With engine running, check fluid level on dipstick (should be in HOT range). Add additional fluid as needed to reach proper level, checking frequently to avoid overfilling.
    ⚠Do not overfill transmission. Overfilling causes foaming, overheating, and potential transmission damage.
11. 11

    Inspect for leaks
    With engine running and transmission at operating temperature, carefully inspect all connection points at transmission housing and radiator/cooler. Check along entire length of cooler lines for seepage. Look for drips or wetness indicating leaks. If any leaks are found, shut off engine, allow to cool, and re-tighten connections or replace faulty seals.

Reassembly

1. Reinstall front splash shield/under cover and torque fasteners to specification
2. Lower vehicle from jack stands and remove wheel chocks
3. Verify final fluid level with vehicle on level ground, engine at operating temperature, in Park
4. Top off ATF if needed to reach proper level on dipstick HOT range

Verification

• Start engine and verify no leaks at any cooler line connections with transmission at idle
• Test drive vehicle for 10-15 minutes, including highway speeds to fully heat transmission fluid
• Re-check all connection points for leaks after test drive with engine running
• Verify transmission fluid level is in HOT range on dipstick with engine running, transmission in Park
• Confirm smooth transmission operation through all gear ranges with no slipping or delayed engagement
• Inspect ground under vehicle after overnight parking to confirm no fluid leakage

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