Bad A/C compressor -- Do I really need to flush the system?

[wakingtowinter]

Looks like my A/C compressor is toast. It makes a terrible grinding/growling noise when I turn on the A/C. Took the belt off and the clutch spins freely but the main bit turns roughly, like it's catching on spots. Idler pulley doesn't feel great, but spins freely and doesn't feel like it's near seizing.

 

I've read that once a compressor bearing goes bad, all kinds of metal debris can be introduced into the system, thus the need for a flush before the new compressor is installed. Is this really necessary? I don't think I can do the flush myself--looks like you need compressed air and I don't have that. I was hoping to just toss in another compressor and charge it with a can from the store. Is it necessary to replace anything else like the condenser or drier?

[Crazyeights]

They sell 'quickflush' kits just about everywhere.

[DaveT]

You also need a vacuum pump to remove air and moisture from the system after you put it back together.

[1 Lucky Texan]

sounds like your compressor is past any easy fixes - but there's still some good reading here;http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/43428-diy-c-air-conditioning-leak-refrigerant-repair-5-less-15-minutes-less.html?highlight=diy+compressor+o-rings+valve

[idosubaru]

there's no need to vacuum the system - i haven't in 10+ years and never had a problem, waste of my time at this point on most older Subarus.  but sure, if you want to tear it up, just don't feel like you must. 

 

i've swapped compressors, charged, and run them before without issues - it depends what is failing interally, but the "debris everywhere" stuff everyone talks about online is more theoretical jargon and possibilities than definitive outcome.  most people writing about A/C stuff online aren't very well versed in what they're talking about - even if they're professionals, trained, etc, and carry a dogmatic view about it - so it's hard to wade through your options. 

 

i've never flushed a system and never had issues.  not saying it's wise or not risky, i've just never had it happen - even when swapping a failed compressor - so all the naysayers would have recommended the wrong thing for those vehicles and situations. 

 

here's two rough recommendations: 

 

here's what i would do - if you have ample supply of used compressors - they're a dime a dozen for EJ vehicles because they rarely fail/there's no demand (i'd give you one if i had them because they're pointless to try and sell - but alas i've already given them all away/thrown them away):
1.  pull the compressor and line from compressor to condensor - since you'll want to replace those orings anyway - it's like no extra work. 

2.  flush those lines into a bucket.

3. if in step 2 you get residual bits of metal showing in the bucket then you need to address the entire system

4.  if you get nothing then install new orings, new schrader valves, bolt everything back on and charge it without vacuuming.

5.  so basically it's a $50 or less fix and only takes a few minutes. 

 

if you're installing a new compressor or can't find any cheap ones then yeah flush the entire system so you're not putting the compressor at risk.  though if you flush the lines and condensor up front into a bucket and see no debris i wouldn't worry about doing the entire system thing myself. 

[Crazyeights]

Agreed ^^^ this methodology works fine in most cases

[Fairtax4me]

If the compressor has failed internally it has thrown metal particles though the condenser all the way to the filter drier. 

The condenser on these cant be flushed due to the design of the core. It has to be replaced if it has metal in it. There's no way to completely remove all of the metal from the condenser. 

 

You can flush the hoses with an AC flush solvent. The drier and condenser need to be replaced. 

[Rooster2]

I totally agree with Grossgary's post. If you don't find metal particles as described in steps 2 and 3, then install a used compressor, and follow step 4. The only thing I might add, is if not vacuuming the system before R-134 re-install, then do this. Add about a half a can of 134 into the system, that should be enough to activate the compressor. Run for a short amount of time, then shut off the system and vent out the half can of 134 to the atmosphere at the low port schrader valve. This, I feel, helps vacate some of the atmosphere, and moisture that may have entered the system, while it was "open." I then install 2 cans of 134, and job is done. 

 

Also, while the system is open, I try to plug openings to keep moisture out of the system where ever possible. Yea, I know wantonly venting 134 to the atmosphere is red neck, but for just a half a can, I don't feel too guilty. I had to open the system on my 99 OBW about 3 years ago. After recharging as described, my system continues to pump out good cold air, so I must have done something right.

[wakingtowinter]

Wow, all right, that's what I wanted to hear! Thanks everybody. You really don't need to vacuum the system? Is there something particular about these cars that makes it unnecessary?

[Crazyeights]

Because these are small fairly simple systems probably. For example you might need a vacuum pump on a system with front and rear evaporators, lots of long lines, etc.

[Fairtax4me]

It's not "unnecessary", because even though the system is small air and moisture in the system does lower the cooling efficiency, but the difference is small enough that it usually doesn't matter.

The drier can usually remove enough water from the system to cancel any effects it may have.

Air in the system raises the system pressure and decreases its ability to cool. Removing the air by vacuuming or purging the system returns it to its optimal efficiency, but the difference is small enough with most systems that most people will probably never notice.

 

Too much moisture in a system can cause icing to occur on the expansion valve or orifice tube and cause it to stick or totally freeze over and become blocked. This generally only happens if the desiccant in the drier has been exposed to high humidity atmosphere for a long period and has become saturated.

On a system that has been open for a long time, the drier should be replaced, even if you have the system vacuumed. Last one I bought was $15 on rockauto. Might not be that cheap for every subaru, but in general they don't cost very much.

Edited July 3, 2016 by Fairtax4me

[1 Lucky Texan]

vacuum could also demonstrate there's still a leak that needs to be addressed - but, gg's experience is that, the majority of time, a vacuum session is unneeded.

 

I suspect it may depend on factors like ;how long and how - 'severely' - the system may have been exposed to the atmosphere, catch it quickly and there' not much moisture inside. probably the older a system is, the more o-rings that may need to be addressed. Also, if the system has had to be re-charged multiple times, it may have a little more moisture in it, etc.

[Theophilus]

It may not be strictly necessary, but if you're going to be working on your A/C system anyway, I don't know why you wouldn't vacuum it out.  You can borrow the pump and manifolds from AutoZone for free, and they'll even let you borrow a bottle of pump oil to replace whatever gets used.  So your only cost is the tiny bit of electricity to run the pump, and it can end up saving you money in the long run if it finds a leak before you waste two cans of R134a refilling the system.