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Old 05-02-2018, 03:23 PM   #1
Scooby Newbie
Member#: 71202
Join Date: Sep 2004
Location: Boca Raton / Miami, FL
2005 Impreza WRX STi

Default Help with ac leak 2005 STi

Hello all,

My 2005 STi finally met its first winter this year. Now that summer's coming back, I tried turning on my a/c a couple days ago and got no cold air.

The compressor was not turning, so I bought a can of 'freon' and added some to the low pressure line. Sadly, the pressure never went above 20psi and eventually I noticed green liquid at the point where the low pressure hard line returns to the compressor.


I assume it's green because when I had the 'freon' topped up last summer the guy added dye to try and find a leak. He found none and we assumed that some prankster had released my 'freon'... especially because the a/c worked fine for the duration of summer.

While researching the next steps, I found this forum site:

Looks simple enough.
1. disconnect hard line bolt
2. replace o-ring
3. reconnect hard line bolt
4. refill at low pressure line

Any thoughts on this?
Anyone know the details of the o-ring I need?
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Old 05-04-2018, 12:43 PM   #2
Scooby Newbie
Member#: 71202
Join Date: Sep 2004
Location: Boca Raton / Miami, FL
2005 Impreza WRX STi


Nah screw it. I'll let the dealership swap the o-ring and refill the system.
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Old 05-04-2018, 02:30 PM   #3
Scooby Newbie
Member#: 151245
Join Date: Jun 2007
Chapter/Region: South East
Location: St. Pete
2006 WRX Wagon


On my 06 i’ve had the o-rings done by dealer and I’ve had the Schrader valves replaced. System has to be drained for either service I believe.
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Old 05-06-2018, 03:50 PM   #4
Samurai Jack
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Member#: 21145
Join Date: Jul 2002
Chapter/Region: NESIC
Location: Not in my own time
2002 Enemy of Aku


Presuming there is any freon left in the system, the system will have to be drained for 2 reasons:
1. It is illegal to vent freon to the atmosphere. It has to be evacuated via a machine.
2. The freon can be captured and re-used.

There are maybe seven (7) o-rings in the system.
First thing will be to re-charge the system with a did and look for a leak, otherwise you could spends hundreds or thousands of dollars ==s chasing ghosts until you find the right place with the leak.
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Old 05-24-2018, 03:09 PM   #5
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Member#: 71108
Join Date: Sep 2004
Chapter/Region: SCIC
Location: San Diego, CA
2005 (Sold) WRX STi
Crystal Gray Metallic

Default Replace o-rings

Not sure if you're already dealt with this...but anyway...

I have successfully repaired the system on my 2005 STi a couple times.

The way you describe it, the low pressure return to the pump, is the first place my car failed. I think the high pressure side was also weak. The o-ring becomes compressed and weak and a little bit of vibration eventually breaks the seal. The heat in that area doesn't help either. However, because refrigerant is expensive, I recommend (based on my experiences) that you replace EVERY o-ring you can while you're at it, not just the one that failed.

On my car, I purchased several green o-ring kits (the HNBR (hydrogenated Nitrile Butadiene Rubber)) variety, which I think is probably a little better than the factory Buna-N type, but who knows). You can learn as much as you want about o-rings online, it is really a science, but if you just get the green HNBR variety These are available at auto parts stores, RockAuto, etc. HOWEVER, I have not ONCE had a kit that actually contained every single required for the system. So you get multiple kits (different kits)! They're not expensive. So, look around (I think RockAuto is probably the easiest option), and then buy two kits. You'll waste a lot of o-rings, but oh well. It's less than $10. I do NOT recommend you get a generic box of o-rings, because it will almost certainly be useless. Just get o-ring kits specifically for your car, and get MORE THAN ONE. Even if it says it has every ring, it probably won't.

On my system, I also replaced:

Expansion valve (accessible from passenger footwell without removing the dash, but you do have to remove other parts). It's not expensive.

Receiver drier (this is a must if your system has been at atmospheric pressure (gauge pressure 0) for any length of time). It's not expensive ($12).

Replaced the hybrid hard/soft hose on (I think) the high pressure side. Might have been the low pressure side, but I don't think so, and I don't remember. It was leaking in a way that was impossible to find. This is EXPENSIVE, from Subaru, but I could find it nowhere else.

I wouldn't add a lot of oil unless you know you have lost some. Make sure you use the right type of oil if you replace it, there are different types, and it matters. You want a little on hand to lube up the o-rings.

Replaced the valve cores. This can easily be done with the system depressurized, but it can also be done with the system pressurized, with a cool little valve replacement tool (which is something like $20-$40). I recommend not cranking down the screws on your A/C Manifold gauge, tightening just enough to open the valves, to avoid damaging the valves, when working on the system/filling the system. I have found that over-opening the valves seems to result in leaks down the road.

As far as o-rings, I replaced every single one I could find. There are the ones at the compressor, there are multiple rings on the receiver dryer, multiple rings on the expansion valve, and if you trace out the hardlines you'll be able to find a couple other small rings to replace. If you have the FSM pictures, you'll be able to identify all the places you need to access and open.
The most challenging part of the whole job is to get the right match of the o-ring to the one you're replacing. It's really hard, because many of the rings have nearly the exact same ID/OD, with slightly different diameter. This is one of the reasons I recommend you have a fantastic array of o-rings available. Otherwise you'll find yourself in a situation where you don't have the right one. Starting with a kit specifically for your car will help ensure that you should have the correct rings available. And multiple kits will ensure sufficient quantities.

You need to do the o-ring work with perfectly clean hands. You don't want to get dirt into the system and you want the o-rings to be clean. Wear a separate set of clean gloves after you loosen connections when actually putting on the o-rings, and have a lot of clean paper towel available to wipe things clean. Don't use screwdrivers, and if you do make sure you don't scrape any of the aluminum. Use plastic pry tools if you can.

When everything is done, you have to vacuum down the system and make sure it holds. And hold vacuum for a while to make sure any moisture in the system boils off. You'll need a real vacuum pump.

After I did this work, the system has held pressure for the last couple years. So it seemed to do the trick.

Trying to remember anything else I learned...

Anyway, parts list:

Refrigerant - preferably without oil, and without dye, unless you want dye. You'll want to have a couple cans. And you'll need the special adapter that allows you to open the can and introduce refrigerant via the manifold pressure gauge.

O-rings (multiple kits, lots of o-rings SPECIFICALLY for your car - don't get a generic box)
Receiver Drier
Valve core kit (there are at least two types of valves, make sure you get the right one).
Expansion Valve
Extra hybrid hose, if needed. (From Subaru)
Refrigerant oil if necessary (you'll want a little to lube up the o-rings)

Manifold pressure gauge.
Vacuum pump. A good one would be nice.

Don't overtighten any of the bolts. It's all soft aluminum. It's 7.4N-m (5.4 ft-lbs) for small o-rings, and 15N-m (10.8ft-lbs) for large o-rings, in general.

Follow the factory service manual for charging the system.

Good luck.
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Old 05-25-2018, 02:44 PM   #6
NASIOC Supporter
Member#: 30669
Join Date: Dec 2002
Chapter/Region: Tri-State
Location: USA, North NJ, 07456
1998 Legacy 2.5GT
Silver Sleeper BK, 5MT


alanicit, basically (from what I know of automotive AC.....), absolutely excellent post.

Yes, pretty much ANY connection with O-rings you open, assume you will replace them. If they are sorta new (maybe a few months?), they may be OK.

If the system has been open for a bit, really need to replace parts (including O-rings and then some), vacuum down, check for leaks, fix as needed, then charge.

Only issue with replacing bits is breaking fasteners.
Open system, it is just a PITA and cheap dollars.

Great post overall though, thanks. Hope others find this.
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