Transmission Cooler Leak

A transmission cooler is a kind of small radiator that is filled with hot Automatic Transmission Fluid (ATF) that is pumped from the automatic transmission to the front of the vehicle for cooling. Sometimes transmission coolers are part of the same assembly as the radiator or somehow linked to the engine's cooling system. Any leak in the system can cause severe damage the vehicles engine or drivetrain.

Table of Contents

• 1. Symtoms
  • 1.1 Transmission Harsh Shift
  • 1.2 "Strawberry Milkshake"
  • 1.3 Puddle of Red Oil on Floor
• 2. Preventative Measures
  • 2.1 Service Regularly

Symtoms

Transmission Harsh Shift

A leak in the transmission hydraulic lines that travel to the transmission cooler can empty a transmission of fluid at a slow to even dramatic rate depending on the size of the leak. Any automatic transmission that looses or has less fluid than it needs to run properly will most likely be coupled with a harsh shift in all gears, or if left unattended it can cause transmission slippage.

"Strawberry Milkshake"

In referring to a strawberry milkshake I don't mean an actual milkshake, but more what coolant and transmission fluid look like when mixed together. The red ATF will typically overwhelm the color of the coolant. If the engine cooling system and ATF cooling system are part of the same assembly or cross each other somehow, than there is a possibility for that seal between them to corrode or break and leak ATF into the coolant and coolant into the ATF. When this happens the engine may overheat, transmission start slipping or shifting harshly, and you should see a Strawberry Milkshake like liquid in the radiator cap or coolant reservoir.

Puddle of Red Oil on Floor

Now a transmission fluid leak from one of the cooler lines can leave a dripping on the floor when the engine is off or if the car sits for a while, it should only leave a dripping because the fluid is not under pressure.

If the engine is started and the transmission fluid starts flowing and pumping, than the drip will accelerate like a hole in a garden hose it will turn into more of a trickle or a pour depending on how severe the leak is.

Transmission fluid leaks should be treated seriously and repaired promptly to avoid permanent damage to the transmission.

Preventative Measures

Service Regularly

To prevent premature corrosion, wear, or damage to your engine or transmission cooling systems regular flushes of the coolant and ATF are strongly recommended. Intervals are typically every 30,000 to 60,000 miles for most cars depending on factory recommendations. Flushing coolant can keep it from becoming too acidic and breaking down over time, the older the coolant the more acidic it becomes, and the more damaging it can be to your engines cooling systems and any gaskets or seals involved.

Regular flushes of the ATF in your transmission are recommended because it gets all the metal grit and clutch dust out of the fluid, which can collect in areas like the cooler or valve body and cause corrosion or damage. Flushes are also good for maintaining seals and gaskets from cracking or wearing over time.