Symptoms
Coolant weeping from the bottom of the radiator — the driver's-side bottom is a common failure point on 4th gen V6s — or an old original radiator you don't trust with transmission cooling.
The fix, step by step
- Remove the top trim and (optionally) the front bumper for access.
- Drain the radiator, unbolt the overflow tank, disconnect the transmission cooler lines on the driver's side (keep them upright), unbolt the fan shroud and the four radiator mounts, and lift it out.
- Mount an external cooler on the condenser, route the transmission lines through it, fit the new radiator, refill and bleed, then check transmission fluid level.
Tools & part numbers
- Metric wrenches to 17 mm
- hose-clamp pliers
- drain pans
- radiator
- Hayden-type transmission cooler and hose
Where to buy the parts
Radiators & transmission coolers — 2004 4Runner catalogRockAuto ↗
Hunting a used or discontinued part? Search eBay Motors for Toyota 4Runner 4th Gen parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.