Refrigerant is NOT supposed to leak out. The molecules are big enough to not ooze through rubber lines, but with movement of those hoses, heat/cold cycling, people leaning on them checking the oil, etc., the hoses will get small cracks in them that will allow the refrigerant to leak. Service the system, and you run the risk of making the Schrader valves leak, too. It seems that the design of those quick-connect ports was not that good, and are prone to developing leaks over time. You'll need a special 5-point socket to change them out. They're not that expensive, but you can't change them with the system charged, so it's probably best to let a pro do it since they'll be able to recover the refrigerant, pull a vacuum on the system after the change out and have the special tools to swap them out.
Who said. That it's supposed to leak..?
I say due to their size, their design, and the relatively large number of components with interfaces—allowing for the replacement of lines, condensers, compressors, dryer cartridges, or expansion valves—car air conditioning systems are much more prone to leaks and cannot be compared to refrigerators.
Air conditioning systems sometimes develop leaks as they age. If they require servicing every three years, that's to be expected. Of course, if the system runs dry after six months, you have to search for the leak, which can be quite time-consuming.
And having it done at a garage is probably very expensive, as replacing parts can easily cost $2,000, while a service every three years costs around €80, at least in Germany.
Refrigerators don't have this problem. Refrigerators easily last 20 years, and if they leak, they're essentially scrap.
Therefore, the statement that: Car air conditioning systems should be leak-proof is technically spoken correct.
. ... At the same time, it's also true that they often aren't.
When I get a vehicle into the workshop with a broken air conditioning system, the first thing I always check is the refrigerant level. Usually, it's low. If it's a third low, I figure it just needs a service, so I refill the refrigerant and that's that. Even with empty systems, I first create a vacuum and hold it for a while to check for leaks.
And if it's airtight, I refill the system.
Of course, if the customer says it only lasted three weeks, I look for the leak, and it's usually the condenser that's faulty; less often it's other components.
To make this diagnosis easier, I always add oil with a contrast agent so that when the system is empty after three weeks, I can use a UV lamp to see exactly where the leak came from.
The Schrader valves are very easy to replace. If one is leaking, you unscrew it with a special tool and screw in a new one. I have a whole box of that in stock.
