why does my dog drool uncontrollably only when riding in a car?

Because she's car sick. To help her get over it, take her for a few very short drives, with something fun at the end of it like a walk, or playing in the park, then back home. It helps a lot of dogs if they can see out the window. If her rides are fun, she should get over it.

She's probably anxious and nervous. You can try putting her in the car, but not go anywhere. Turn it on, put her in, and then get in yourself like you would if you were going for a ride. Keep the car in park and see how she reacts. If she doesn't start drooling praise her and give her treats. If she does, take her out and try another time for a shorter period. Soon, she'll get used to the car and you can try driving around the block. If she starts drooling again, you'll know you've gone too fast, so you can go back to keeping the car in park. She'll find that car rides are a good thing. Good luck!

She's nervous or nauseated. Lots of dogs are very fearful of riding in a car and many get car sick too.

no.. normally dogs dont drool when they are hott.. they pant... but dogs do sometimes drool when they are eather nervice or excited.

hot

SHe might be hot.