Solved?; AC - Hissing Sound

[Cronenberged]

When I turn my AC on there’s a hissing sound coming from inside the dash. Also, the right side blows hot air and the left side cold air. Looking for anyone who’s experienced and fixed this issue or dealt with it. Thank you!

[toy4to]

You have a refrigerant leak somewhere. I had the same issue a while back. Once you add refrigerant, the hiss goes away. The main thing is to find the cause of the leak.

[Halftim3]

I have the same symptoms. Also blowing cold on left, warm on right, but sometimes still cold through all vents. I'm planning to have the system recharged and from a little research I'll first have the system evacuated, then I'll be replacing AC receiver drier part# 64538377330 and expansion valve part #64503452759 with an o ring kit. Then go have it recharged probably with some dye to help track down a leak.
These were some threads i read

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/20703-r134-capacity/page2

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/51668-ac-blows-warm-air-through-one-vent-even-with-new-compressor/page2

[sapote]

You have a refrigerant leak somewhere. I had the same issue a while back. Once you add refrigerant, the hiss goes away. The main thing is to find the cause of the leak.

Could be just low refrigerant but not a leak. A proper charge would fix the sound.

[Cronenberged]

A buddy of mine mentioned it might be the schrader valves, anyone have a part number for them or are they universal?

[sapote]

A buddy of mine mentioned it might be the schrader valves, anyone have a part number for them or are they universal?

you mean slow leaking valve leading to low refrigerant then hissing, or the valve making the hissing?

[Cronenberged]

you mean slow leaking valve leading to low refrigerant then hissing, or the valve making the hissing?

Slow leaking valves leading to the low refrigerant. I believe the hissing sound is as mentioned earlier is due to the low refrigerant.

[George Hill]

The car is low on refrigerant. The hissing is from the low volume of refrigerant flowing through the expansion valve. The reason it only cools on one side is because the refrigerant enters the LH side of the evaporator and has lost its cooling efficiency by the time it makes it to the RH side.

Schrader valves do leak, but its not common in my experience. You can drop a little water in the Schrader port and see if it bubbles.

But it probably needs an evaporator. I've replaced at least 100, maybe 150 evaporators, ultra common in Texas IMO it should be considered a 4th in the "big 3."

If the car doesn't have dye in already (it wouldn't from the factory) you'll still see some oily residue in the area of a leak. Start by inspecting the Schrader valves and the compressor. If nothing there then you can access the blower motor cover, look past the blower motor and if there is any built up dirt a debris in the middle of the evap it needs to be replaced.

You can add dye, but in my experience dye is not always visible on the evap from the engine bay side. It will show on the engine bay side though, but in my experience is almost always an evap. Compressors are next on the list, but not very common comparatively speaking. Everything else is pretty rare.

[Halftim3]

Without replacing the evaporator and just replacing the expansion valve and drier, assuming the leak is from the evaporator, how long could we expect a new recharge to last?

[George Hill]

Without replacing the evaporator and just replacing the expansion valve and drier, assuming the leak is from the evaporator, how long could we expect a new recharge to last?

IDK why you'd replace the exp valve and drier if the leak is in the evap.

But as far as recharging it without fixing the leak and how long that will last, its anybody's guess.

[Halftim3]

Isn't the expansion valve and drier must replace items if the system gets discharged, more so the drier?

[George Hill]

Drier is supposed to be replaced if the system is open for 24hrs. Whether it NEEDS to is a matter of debate. I generally pull a long vacuum on cars if theyve been open awhile. No known issues have come of that. *BMW driers are very expensive, ACM makes a "cheap" drier that comes from Germany, everything else is Chinese. I'm not sure an old BMW drier with a long vacuum is worse (or better) than a Chinese drier.

Dealers/shops like to sell expansion valves because there is no additional work but they get they extra parts margin.

IF you have a compressor fail then YES, replace the drier as it could have put debris in the system which should be all caught in the drier.

[Cronenberged]

George Hill it was a Texas car for last 20 years. Avoiding the evaporator swap for now. It’s quite affordable for me to use my bases services so I had the system extracted as well as vacuum and leak tested for 40 min; zero reports from the snap on system. Then filled it with 26.01oz of refrigerant blowing ice cold again. It was over pressurized from the previous owner so that could have been the issue.

[Halftim3]

Glad you got it blowing cold OP, just wondering if you went about replacing the drier and/or the exp valve in your process?

[George Hill]

Personally I've never seen a leaking evaporator fail a vacuum/leak test even when they are physically bad. In my experience if it fails the vacuum test there's a visible hole, pinched o-ring, etc.

How much was in the system? Evaps generally leak down to 0.3-0.4# and don't get any lower than that for some reason. ***E46s hold 1.63#