Mystery Fluid
 

I've been looking into purchasing an '83 Rx7 GSL from a private party somewhat nearby. I went to check it out the other day while it was raining and I noticed a small rainbow puddle coming from under the car. I ignored it for the time being and got to look at the rest of the car. After about 10 minutes of running the car in the driveway I noticed the rainbow puddle had gotten much, much larger. I tried to wipe some up with my finger to see what kind of fluid it could have been. I honestly couldn't tell that there was anything on my finger but water. The owner is insisting it is coolant because he's said just recently the coolant light came on but I've never witnessed coolant to cause a rainbow in rainwater before. It definitely wasn't greasy or colored, and it smelled like nothing at all. Any idea what this could be? Any help or input would be greatly appreciated, thank you!

Sounds like a mixture of water and oil leaking from your broken water seals or cracked hounsings/irons.

Coolant and oil have known to mix together when there is a coolant housing leak surrounding the rotors.