thats what its intention was for, but if you have a leak you suck moisture into the system. the sealer reacts with moisture to actually become a solid so any moisture that has crept its way in due to a leak will end up turning solid where ever the sealer and moisture meet at. Condensor, evap core, expansion valve, in an a/c line or where ever. once you haev that in there and it has gone through its chemical reaction and has become a solid, if it breaks loose anywhere you all of the sudden have a small bullet flying around in your a/c system unless it gets lodged in a filter or in the orfice tube if your vehicle has one. its been known to actually clog up an a/c system to the point that it wont cool anymore either after causing major restrictions throughout the system or gumming up a compressor to teh point it can hardly turn and almost locks up. Remember, an a/c compressor is a pump as is your engine. would you like your compressor or your engine chewing up solid chunks of shit? would be like dropping a bolt down the throttle body of your car.
Since i am getting all super descriptive here, let me clue you in on another thing with r134a. IT'S GONNA LEAK IN SMALL AMOUNTS NO MATTER WHAT YOU DO. Back in 96 and 97, the mobile air conditioning society had thier hands full testing what they thought were manufacturer defects on a shit load of under warranty compressors (r134a started to be used in the 93-94 model years). Come to find out, it wasnt a compressor problem at all. a r134a molecule is 1/200th the size of the old R-12 refrigerants molecule, therfore it escapes out of small seal sepage leaks extremely easy as well as general expansion and contraction due to temprature changes (think of what your underhood temps do during the winter months). Over the period of a year, the average A/C system on a newer car using r134a will leak 1 to 2 ounces. dont seem like shit does it. it wasnt with the old r12 stuff but a 1 to 2 ounce low charge can cause a 60-80 percent loss of oil movement through the a/c system. An a/c compressor requires oil just like the engine in your car does so whats gonna happen if you starve your cars engine for oil? It's gonna lock up eventually or become extremely noisy and work innefficiently.
The newer cars using r134a refrigerant are a critical charge as you can see if they stop moving oil significantly with being 1 to 2 ounces low. This means they are a critical charge system and have to be charged to exact specifications. The gauge on your can of refrigerant from walmart can get you close but not exact if you know what you are doing. The old pressure charts dont work for 134a. The old sight glass trick dont work on 134a. you have to completely suck the car down into a vacuum and refill it to get the charge weight correct or you are starving the compressor for oil even though you think you just recharged it how it should be because that cheap ass gauge said you are good.