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removing flush from evaporator

Mercury7 on Thu September 02, 2010 9:19 AM User is offline

Year: 1998
Make: Chevy
Model: Cavalier
Engine Size: 2.2L
Refrigerant Type: R134a
Ambient Temp: 70F
Pressure Low: n/a
Pressure High: n/a
Country of Origin: United States

My ac system needed serious attention as compressor (noisy/shot drive belt pulley bearings) and condensor (hole in it) needed replaced. Have purchased new parts - kit that incl. compressor, accumulator, orifice tube + PAG150 oil, and a new condensor. Have taken apart the entire ac system except for the evaporator, which was left on the vehicle (a royal B to remove), and purchased an aerosol flush (A/C Pro Power Clean & Flush) at an auto parts store. The tubing was flushed out quite easily since it was out of the vehicle, and I've flushed the evaporator which seems it really wasn't very 'dirty' at all to begin with. I've been blowing out the evaporator to purge the flush solvent, holding the air gun snug on the inlet and plugging the outlet with my thumb (wearing a disposable glove on that hand for a better seal). While nothing is physically dripping from the outlet anymore, I can still see (and smell) the cloud of solvent coming out when I release with my thumb.
My trouble is that I have been at this for a few hours now (spread over a few days) and at times it seems there is no end in sight. Question is, do I keep purging until the 'cloud' is completely no more (it is starting to 'thin' a bit but I can still see it), or is there something else I can use to get the remaining solvent out of the evaporator? I'm beginning to get a little impatient with this however, and can hear the temptation to just put it all back together and evacuate the system, but (so far) have refused to listen and continue to purge. Am also using unfiltered shop air, which I know (from reading these forum posts) is not a good thing, but is all I've got right now. Would it be better to introduce a new chemical to purge the flush solvent from the evaporator, perhaps even renting a 'shop-grade' compressor with an air filter on it or maybe even purchasing a nitrogen canister? While most of the flush solvent is gone now, I fear if I give into tempation to reassemble, I'll most certainly risk all the time and money I have poured into this thing.
Taking my car to a shop is never an option, as bad luck with such things frequently befalls me, and damage of some kind to my vehicle(s) is quite often the result. For this reason, I've been doing repairs myself to every car I have ever owned for last 30 years, save only transmission trouble and new tires (which damaged my exhaust system once before and resulted in body damage on another). No one touches my rides but me. Would appreciate any suggestions/advice you might have.
Thanks Much!


GM Tech on Thu September 02, 2010 9:52 AM User is offline

This is why I never flush for a leak- A quick check of compessor oil would reveal necessity for a refrigerant flush. I never introduce anything into an a/c system that I don't want in there or can't get out. If I flush, I use 134a refrigerant- A V-5 system rarely fails in a manner that will require flushing. Most often there is a leak- as you discovered-- if you fix the leak, (replace condenser) then the noise from the compressor would have probably be gone....if it is from the compressor body. If noise from compressor is in drive pulley area-- then you probably have the V-5 classic clutch drag problem- which is easily fixed. If noise is compressor pulle bearing, then that too, can be replaced.

In my opinion, you made two mistakes, you decided to flush, and you used a flushing agent that you can't be sure you can get it all out.....

Most will recommend an extended vacuum to force flushing agent to vaporize.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

HECAT on Thu September 02, 2010 11:24 AM User is offline

I mean no disrespect but trying to flush component this way is a joke; I will explain.

If it is the Wynn's A7801 "A/C pro power clean and flush" then you are in luck as I see (from the MSDS) nothing wrong with the composition of the chemical; the problems you are having are related to the method.

The can does not contain enough liquid flush, pressure, or a large enough discharge path to produce an effective flush; that is why you have not seen much result from this effort. We call this a "poof" and not a flush; what you have now is flush chemical you have added to the remaining oils that were in the component.

Next the OSHA regulated orificed (.030") blow gun is not allowing enough air volume to force evaporation to occur, and being mixed with the remaining oils is also going to further limit evaporation.

My suggestion is to attach your air line directly in some manner to allow for the maximum air flow path and blast this component for 30 minutes or more. If you don't have a compressor capable of keeping up; you are going to need to get one.


HECAT: You support the Forum when you consider for your a/c parts.


Edited: Thu September 02, 2010 at 11:26 AM by HECAT

Mercury7 on Thu September 02, 2010 11:29 AM User is offline

Unfortunately, I can't use refrigerant as a flushing agent since I don't have a recovery system (am just your average do-it-yourselfer). By the time I got to this problem, the system had already been empty for quite a while. My third mistake was throwing money at this problem before I had researched it enough. Same 'voice' that is telling me to just reassemble right now is same one suggesting vacuuming the system (think I bought one deep enough to do the job) and just leave overnight (at least) in hopes of removing what little flushing agent that is left in there. Is also the same voice that suggested just purchasing a smaller drive belt for just a few bucks (bypassing the compressor) and simply roll the windows down in summertime. I hate to live with such compromises though, especially when its 90+ outside.
Appreciated the feedback - Thanks!

Mercury7 on Thu September 02, 2010 11:44 AM User is offline

HECAT - That makes perfect sense, since the 'cloud' only appears right after I remove my thumb from the outlet tube. After that, the airflow drops sharply, and cannot be sustained at a high enough level due to the size of the opening on the air gun and perhaps the (pitiful) capacity of the air compressor. Will look into getting larger versions of both.

HECAT on Thu September 02, 2010 11:48 AM User is offline

The potential amount and type of solvent you have in there will be slow to respond to vacuum. If you try your unattended overnight vacuum process and there is indeed a volume of solvent; you could contaminate the vacuum pump oil and find the pump burned up in the morning. Vacuum will flash off the residuals, only after the majority has first been forced to evaporate under a long hard blow.


HECAT: You support the Forum when you consider for your a/c parts.


bohica2xo on Thu September 02, 2010 12:24 PM User is offline

Go to your local pull it yourself junkyard, and locate a tube or hose on a GM vehicle with the proper fitting to mate with the evaporator line you are blowing into. Cut/saw/rip/use light sabre - all you want is the last foot or so & the fitting.

Once you have the mating connector for your evaporator, you need to attach an airline coupler of the type you use in your shop to the other end of it. usually a hose barb & a clamp will do it, but if you have a metal line you may need to do a bit more - like use a short piece of hose & two clamps.

Attach the fitting to the evaporator. You might want to put a large hose (like a piece of garden hose) on the evaporator outlet to direct the flush in a safe direction.

Let the compressor run until full. Snap the quick coupler onto the evaporator line, let it roar until the compressor is down to 60 psi or so, then disconnect. Repeat as necessary. I blow until I can't smell the solvent at discharge line.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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