[JFP in PA]

First of all, the Uview gauge reads in inches of vacuum, not PSIG. Secondly, vacuum should not move the liquid in the system, unless the liquid is being pushed by entrapped air behind it that is trying to get out. We use one of these systems just about daily, and the only time we have ever seen coolant liquid pulled by it is when there was air still in the system that was moving towards Uview unit. If that happens, you need to “throttle” the air pressure to the Uview unit so that the vacuum level comes up more slowly to allow the air pockets time to escape. We always pull vacuum until the system is at 25-27 inches, where we hold it to test for leaks.

Contrary to what I have seen published online; the Uview system is incapable of moving liquid unless the end of the Uview unit is actually submerged in the fluid, or there is an air pocket pushing the liquid.