* Cracked Engine Block or Transmission Case: This is the worst-case scenario. A crack in either the engine block or transmission case near the mating surface would allow coolant to leak into the transmission. This usually requires engine or transmission replacement or extensive repair, potentially costing thousands of dollars.
* Failed Transmission Cooler Lines: The transmission often has a cooler integrated into the radiator or separate cooler lines running through the radiator. A leak in these lines would allow coolant to mix with transmission fluid. This is a more manageable repair but still involves replacing lines and possibly flushing the transmission fluid.
* Damaged Engine/Transmission Seal: Several seals around the engine and transmission interface can fail. Replacing these seals requires partial disassembly of the engine and transmission, which is a significant undertaking.
* Porous or Damaged Cylinder Head Gasket (Less Likely but Possible): While less likely to directly mix with transmission fluid, a severely compromised head gasket could allow coolant to leak into the engine oil, which then might make its way to the transmission depending on the leak's location and the engine's design.
Because you are seeing a mix of fluids, you should STOP DRIVING THE VAN IMMEDIATELY. Continuing to drive with a coolant leak and contaminated transmission fluid will cause catastrophic damage to both the engine and transmission, leading to a far more expensive repair or complete replacement.
What to do now:
1. Stop driving the van. Continued operation will only worsen the damage.
2. Get a professional diagnosis: Take the van to a qualified mechanic specializing in older vehicles. They will need to inspect the area where the engine and transmission meet to pinpoint the source of the leak. A pressure test of the cooling system might be necessary.
3. Prepare for a significant repair cost: Based on the symptoms, this is likely a substantial repair. Get multiple quotes from different mechanics to compare costs before proceeding.
Ignoring this problem will likely lead to a much more expensive repair or even total engine/transmission failure. Professional diagnosis is crucial to determining the best course of action.
