AC Leak By Right Rear Wheel Well

[Divewire]

I purchased a used 99 Tahoe, with the understanding that the AC system had a leak. I think I have located it and was hoping for some advice on my next step.

I put in some R134a hoping the leak was minor, but I noticed some mist coming from the right rear wheel well. I got a picture, and I am pretty sure the section that the arrow is pointing to, is where the leak is.

The system is pretty well dry, is there a chance I could just replace the coupling/hose and put more R134a in?

Just to note, I am a very novice car repair guy.

 

[letsbangout]

You've probably just got a bad O-ring there. Try copping a set of O-rings for your truck and replacing; Four Seasons makes a kit with a few of every kind.

Now, as to what kind of oil you should coat it with when you replace it, is a subject of confusion for me. I've seen some people suggest using the same kind of PAG oil that your system takes (which you should be adding to the system anyway, since you've invariably lost oil as a result of the refrigerant leak). Others say coat it with mineral oil. An official consensus from an AC expert would be nice, and I don't think you could go wrong with PAG since it has a trace contact with the O-ring anyway, though mineral might be superior in some way.

Also, are you leaking "black death"? Is that gas coming out a dark gray color? I wouldn't just assume it's grease, I would automatically assume it's black death and visually inspect the orifice tube while you're in there (in the liquid line, between condenser and firewall). If it is black death, you'll need to figure out if you're still producing it, fix that, and disconnect everything to blow it out. I've also heard from a GM tech that our condensers are parallel-flow, and you should replace them rather than attempt a flush. Hope that helps.

 

[SunlitComet]

replace the line, use pag oil and get your self a new receiver/drier. evacuate system replenish oil and recharge. the rest of system should be fine.

 

[letsbangout]

If you do replace the line, which isn't a bad recommendation by any means, you might also end up replacing what's on the other side of it at the firewall. In the case of my 99 Yukon and in several others I've read, the factory used hoses with two different types of metal, resulting in threads that quite literally melted together. Amazingly, even though I have a big area on the connection to the rear hose at the firewall where the threads melted together, it still seals up tight and doesn't leak as best I can ascertain with a UV light. But you might not be so lucky. Hopefully that helps.