Safety: Do not keep driving with coolant mixed into the transmission fluid. Tow it if it is pink or foamy.
Checks, in order
- Dipstick checkPull the dipstick with the engine warm and look for pink, milky or foamy fluid. Also check the radiator coolant for an oily film.easy $ · under about $50
- Pressure test the coolerA shop can pressure test the radiator transmission cooler. Many owners just replace the radiator and cooler line seals at the same time.medium $$ · about $50 to $500
- Radiator replacementIf the radiator cooler is the source, replace the radiator and flush the transmission cooler lines. Do not reuse old hoses that are cracked.medium $$ · about $50 to $500
- Transmission flush and inspectAfter the leak is fixed, the transmission needs a full fluid exchange and a look at shift quality. Slipping or burnt smell afterward means a rebuild may be needed.hard $$$ · shop-level job, $500+
Applies to: 1996 to 2002 4Runner with the 2.7L 3RZ-FE four-cylinder and the 3.4L 5VZ-FE V6, 2WD and 4WD, manual and automatic. Where a check only applies to one engine it says so.
Tools and parts for these checks
Links below are Amazon affiliate links: as an Amazon Associate, toyotadata earns from qualifying purchases, at no extra cost to you. Confirm fitment for your exact truck before you order.
| ITEM | USED FOR | BUY |
|---|---|---|
| Radiator for your truck | Replacing a radiator whose internal trans cooler has failed | Shop on Amazon |
| Automatic transmission fluid for your truck | Flushing coolant-contaminated fluid out of the transmission | Shop on Amazon |
| Fluid transfer pump | Filling through the fill or check plug | Shop on Amazon |
| Cooling system pressure tester | Finding coolant leaks and testing the radiator cap | Shop on Amazon |
The same problem on other Toyotas
Other transmission problems on the 3rd Gen 4Runner
More 3rd Gen 4Runner problems
- Clunk, knock or loose feel in the front end over bumps (Steering & Suspension)
- Shimmy, vibration or steering wander at highway speed (Steering & Suspension)
- Frame rust, rotten rocker panels or rusty underbody (Frame & Body)
- Engine overheating or temperature gauge climbing (Cooling)
- 5VZ-FE timing belt service: when is it due and how do I tell? (Engine)
- Turn the key: click or nothing, engine won't crank (Starting & Charging)
All 16 3rd Gen 4Runner symptoms in the interactive troubleshooter →
General guidance from owner experience. Confirm torque specs, fluid capacities and procedures in the factory service manual. Brakes, steering and anything structural: if in doubt, have a qualified shop inspect it before driving.