I've finally gotten around to replacing my receiver/dryer. When I take it out of the box and start removing one of the plastic protection caps to make sure the threads match I hear a loud hissing sound. I crank the cap back tight and open it just a bit to see how long this hissing will go on. I was figuring it's from atmospheric changes from where it was made and shipped. Or maybe it's vacuum sealed for some reason. This thing keeps hissing for a while so I tighten the cap again and here I am looking for what the hell could this be about. It's not even in the car yet, nothing hooked up to it and it's hissing like it's about to go off in my hand. I'm figuring this is normal but want to be sure before I lose an eye or finger or something.

It's for my '91 Accord if it matters. I bought it from Autozone for $25. And I'm replacing it since I've resealed my A/C compressor, replaced all my seals and hoses and this was the last thing recomended since I will next be taking to a shop to have them evacuate and recharge it. There was no failure just a leak somewhere, probably the compressor.

Thanks for the help.

 

Now I'm thinking this could be to assure the purchaser/installer that it has no leaks?

 

It is very important to keep it completely closed until it is installed as you don't want it to get any water vapor in it which could damage it.

You need to replace that every time you open the ac system so you're doing the right thing.

 

That was going to be my other guess. Thanks for all the info.