i have a leak behind the front passenger tire so i had lexus look at it today and they found nothing leaking but saw residual fluid on top of the under panel .my question is,are our engine mounts fluid filled?if so it could be that all the fluid leaked out of the mount so they could not find anything.

 

Take a look at front lower control arm rear bushings, they are 100% oil filled. I changed those before they leaked but were really close to disintegration.
I know that a tranny mount is not oil filled, not sure about the two motor mounts.

 

The engine mount has fluid.