What type of leak?

you can try wynns gear leak stop-it thickens oil and swells the seals.

Standing vacuum test

This happens a lot of times and what we do is fill the a/c system with freon and dye and send the car off so that customer can drive it for however long it takes for the freon to leak out and then have them bring it back in and you will find the leak with the UV light "unless" the leak is in the evaporator then you will need to find some access port to shine the UV light into or check the drain tube for residue.........

where and what is a leak detection pump pressure solenoid on my 97' dodge caravan? On my 1998 Dodge Stratus, it is tucked in between the underside of the car and the fuel tank.