We recently noticed a puddle of transmission fluid under our 1999 Grand Caravan. On closer inspection we found that it was coming from the radiator overflow, meaning that the transmission cooling loop in the radiator must have ruptured allowing transmission fluid into the radiator. I have an external transmission cooler and was wondering if it would be okay to simply block off the transmission fluid lines going into the radiator and reroute the lines form the transmission so that it only uses the external transmission cooler.

 

If the tranny fluid is getting into the coolant then chances are it is happening visversa and coolant is mixing with the tranny fluid. You would stop the tranny leak by going to an external cooler but i would suggest a tranny and coolant flush to make sure there is no cross contamination between the two. Make sure once you resolve the problem with the tranny fluid leak make sure that the coolant isn't leaking from the radiator or you'll wind up replacing it any way.

 

I was planning to flush both engine coolant & transmission anyways because there was a LOT of cross-contamination.
There was never a coolant leak. When the van was started and pressure came up in the transmission it forced into the radiator. We could actually hear it cause the radiator cap to blow and then the level in the radiator overflow bottle would rise and then overflow onto the ground. Of course it was a reddish mixture of trans fluid & antifreeze.
I think that I'll try just bypassing the radiator and going dirctly to the external transmission cooler. Of course I'll need to block off the transmission connections at the radiator. That should still give me sufficient transmission cooling.
Thanks for your reply.

 

Is the transmission fluid pink??? If it is, plan on spending some cash on an overhaul. All of the friction material on the clutch plates in the transmission is made from a water soluble adhesive. It will work for a little while but not long.