Nissan Radiator Leak Coolant in Transmission

By the Radman Auto Repair team, independent auto repair in Etobicoke since 1999 · Updated November 2026

On 2005–2010 Nissan Pathfinder, Frontier and Xterra models, the automatic transmission cooler is built into the radiator. When it cracks inside, coolant and transmission fluid mix, the so-called “strawberry milkshake”. The transmission soon shudders, slips and fails, so catching it early matters.

Symptoms

What Causes It

Before You Start

• Park on level ground, set the parking brake and chock the wheels. Never work under a car held up only by a jack: use rated jack stands.
• Let the engine and exhaust cool before you touch them; coolant systems are under pressure when hot.
• Wear safety glasses and gloves, and disconnect the 12V battery before unplugging electrical parts or working near airbags.
• Check for open recalls on your VIN (Transport Canada or the manufacturer’s site) before you buy parts: a recall repair is free at the dealer.
• Hot coolant is under pressure: only open the system with the engine cold.
• Coolant in transmission fluid damages clutches quickly; don’t keep driving “to see”.

Step-by-Step: Nissan Coolant in Transmission

1. Check the fluids. With the engine warm, check the transmission dipstick; then, cold, check the coolant reservoir for oil.
2. Stop driving if milky. If the fluid is milky pink, park it and arrange a tow or very short trip to the shop.
3. Check your VIN. Ask a Nissan dealer about extended radiator coverage for your vehicle.
4. Drain the coolant. Drain the coolant and disconnect the hoses and transmission cooler lines from the radiator.
5. Replace the radiator. Remove the fan shroud and radiator, fit the new radiator and reconnect everything.
6. Flush the transmission. Drain and refill the transmission several times, driving gently between changes, until the fluid is clean and red.
7. Refill and bleed. Refill with Nissan coolant and bleed the air out.
8. Consider a separate cooler. An external transmission cooler, bypassing the radiator, prevents a repeat.

When to Stop and Bring It In

• The transmission still shudders or slips after several flushes: it may need rebuilding.
• Coolant has been mixed with fluid for a long time.
• The engine is overheating: see overheating and coolant leaks.
• You want the work done under Nissan coverage.

Not sure, or out of time? Radman Auto Repair in Etobicoke does this repair every week. Book online or call (416) 742-4521.

Also Known As

Owners call this “strawberry milkshake”, “SMOD” (“strawberry milkshake of death”), “Nissan radiator failure”, “Pathfinder coolant in transmission” or “Frontier transmission fluid milky”. The part is the radiator with its built-in transmission oil cooler.

Frequently Asked Questions

See also Overheating & Coolant Leaks, Transmission Fluid Service, Transmission Repair Cost, DIY Repair Guides by Manufacturer.

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