Coolant usually enters a transmission through a compromised cooler line, a cracked transmission case, or a faulty radiator (in cases where the radiator contains a transmission cooler).
Here's a more detailed breakdown:
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Cooler Line Failure: Most automatic transmissions utilize a transmission cooler to maintain optimal operating temperatures. This cooler is often integrated within the vehicle's radiator or is a separate unit. Coolant can leak into the transmission if the lines connecting the transmission to the cooler corrode, crack, or become damaged, especially at the fittings. Internal corrosion within the cooler itself can also cause coolant to mix with transmission fluid.
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Cracked Transmission Case: Although less common, cracks in the transmission case (due to impact, stress, or manufacturing defects) can allow coolant to enter if the crack extends into the internal transmission components.
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Faulty Radiator (with Integrated Transmission Cooler): Many vehicles have radiators with an integrated transmission cooler. This design allows the radiator coolant to cool the transmission fluid. If the barrier separating the coolant and transmission fluid within the radiator fails (typically due to corrosion), the two fluids can mix, resulting in coolant contaminating the transmission. This is a common cause of coolant intrusion into transmissions.
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Other Entry Points (Less Common): In rare situations, other compromised seals or gaskets could theoretically allow coolant entry, but these scenarios are extremely infrequent.
Symptoms of Coolant in Transmission:
- Milky or foamy transmission fluid (appears pinkish or brownish instead of red).
- Transmission slipping or erratic shifting.
- Overheating transmission.
- Unusual noises coming from the transmission.
What to Do if You Suspect Coolant Intrusion:
If you suspect coolant has entered your transmission, it is crucial to address the issue immediately to prevent severe damage.
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Stop Driving: Avoid driving the vehicle as much as possible. Continuing to drive can cause further damage.
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Professional Inspection: Take your vehicle to a qualified mechanic or transmission specialist for diagnosis. They can perform tests to confirm the presence of coolant in the transmission fluid and identify the source of the leak.
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Repair or Replacement: Depending on the severity of the contamination and the source of the leak, repairs may involve replacing cooler lines, repairing the transmission case (if possible), replacing the radiator, and/or flushing the transmission multiple times to remove all traces of coolant. In severe cases, the transmission may need to be rebuilt or replaced.
