Q: Should I flush the evaporator that's still in the car?

Background: I'm in a middle of a mid-scale AC reclamation project, and I'm a newbie, but I'm determined to get it done, even if it's going to cost me. AC wasn't working when I bought the car last fall (the AC belt was gone), and a later check showed that all refrigerant was gone as well. There's no conclusive evidence regarding an R12->R134a retrofit. The only evidence is a single quick-connect R134a coupling -- the kind that screws on top of an existing R12 valve, no stickers of any kind, and no PO to ask. The quick-connect coupling is the low-side kind, but it was attached to the high-side valve (being new to the whole AC business, I haven't realized it right away... a bit scary). Practically no oil left in the system -- when I removed the compressor and put it vertically to drain oil, not a single drop came out (a couple of drops came out while I was unscrewing the compressor manifold though). Furthermore, I made things that much worse by screwing up UV dye injection: I had the system evacuated, at 29" vacuum, and attached a Mastercool 10-application concentrated UV die applicator can. The can has a rotating bottom, sort of like a deodorant stick, and the idea is to rotate the bottom one full turn to inject one application worth of die. Well, I plugged the can into the system at vacuum, and it turned out that one doesn't in fact need to turn anything, vacuum will suck in dye without my help, and by the time I realized that, about 8 applications worth of dye went in. So I think a good flush of the AC system is very much in order.

I started taking the system apart and flushing hoses. It doesn't appear like there was much dirt inside, aside from the bright yellow UV dye color, AC flush remains transparent. No solid particles came out. After flushing manifold hoses, I decided to take a leap of faith and flush the condenser while it's in the car. That wasn't a very encouraging experience. I'm using a Mastercool flush gun, and it seems to work as well as a flushing device should, but getting all of the flushing liquid out with the condenser sitting vertically in the car seems hard. I've been blowing air through the condenser for a while, and it looks like it keeps blowing out small amounts of liquid. I'm using special AC flush, and that stuff evaporates a lot less easily that I though it would (I was expecting something like non-chlorinated blade cleaner). I still think that blowing air through the system long enough should get all of it out, but I'm not positive anymore.

With all this in mind, I'm not very enthusiastic about flushing the evaporator (and well and truly reluctant to remove the evaporator just for the flushing). On one hand, there could be some old oil in there (wouldn't be much if there was any though). On the other hand, what if I can't get all of the flush liquid out of there? I've diligently read many, many prior articles on the topic, and I've seen different opinions expressed on the issue of flushing in general and flushing the evaporator while it's in the vehicle. I fully agree that a thorough flushing is a Good Thing, but then having AC flush left in the system would be not so good. Suggestions?

I'm going to put synthetic POE (Auto 100) oil in when I'm done (7 oz sounds like the right amount for a fully flushed system). The plan is to start by putting in R-134a, to see whether the compressor is alive and find any remaining leaks, and then sometime later, when I get some level of confidence in the system, replace it with R12, keeping the oil. Is that a reasonable approach?

PAG oil and 134A contaminated all plastic and rubber in the system.
Replace compressor and all rubber/plastic with new.
Clean interior of condensor and evaporator with acetone, it should take roughly half a quart for each unit.
Danger Warning:
Acetone is dangerous to your health and safety = toxic and fire hazard, please read the MSDS before use.



1. Product Identification
ACETONE
MSDS Number: A0446 --- Effective Date: 04/09/98

Synonyms: Dimethylketone; 2-propanone; dimethylketal
CAS No.: 67-64-1
Molecular Weight: 58.08
Chemical Formula: (CH3)2CO
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3. Hazards Identification
Emergency Overview
--------------------------
DANGER! EXTREMELY FLAMMABLE LIQUID AND VAPOR. VAPOR MAY CAUSE
FLASH FIRE. HARMFUL IF SWALLOWED OR INHALED. CAUSES IRRITATION
TO SKIN, EYES AND RESPIRATORY TRACT. AFFECTS CENTRAL NERVOUS
SYSTEM.

J.T. Baker SAF-T-DATA(tm) Ratings (Provided here for your convenience)
---------------------------------------------------------------
Health Rating: 1 - Slight
Flammability Rating: 4 - Extreme (Flammable)
Reactivity Rating: 2 - Moderate
Contact Rating: 1 - Slight
Lab Protective Equip: GOGGLES; LAB COAT; VENT HOOD; PROPER GLOVES; CLASS B
EXTINGUISHER
Storage Color Code: Red (Flammable)
------------------------------------------------------------

Potential Health Effects
----------------------------------

Inhalation:
Inhalation of vapors irritates the respiratory tract. May cause coughing, dizziness, dullness, and headache. Higher concentrations can produce central nervous system depression, narcosis, and unconsciousness.

Ingestion:
Swallowing small amounts is not likely to produce harmful effects. Ingestion of larger amounts may produce abdominal pain, nausea and vomiting. Aspiration into lungs can produce severe lung damage and is a medical emergency. Other symptoms are expected to parallel inhalation.

Skin Contact:
Irritating due to defatting action on skin. Causes redness, pain, drying and cracking of the skin.

Eye Contact:
Vapors are irritating to the eyes. Splashes may cause severe irritation, with stinging, tearing, redness and pain.

Chronic Exposure:
Prolonged or repeated skin contact may produce severe irritation or dermatitis.

Aggravation of Pre-existing Conditions:
Use of alcoholic beverages enhances toxic effects. Exposure may increase the toxic potential of chlorinated hydrocarbons, such as chloroform, trichloroethane.

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4. First Aid Measures
Inhalation:
Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.

Ingestion:
Aspiration hazard. If swallowed, vomiting may occur spontaneously, but DO NOT INDUCE. If vomiting occurs, keep head below hips to prevent aspiration into lungs. Never give anything by mouth to an unconscious person. Call a physician immediately.

Skin Contact:
Immediately flush skin with plenty of water for at least 15 minutes. Remove contaminated clothing and shoes. Get medical attention. Wash clothing before reuse. Thoroughly clean shoes before reuse.

Eye Contact:
Immediately flush eyes with plenty of water for at least 15 minutes, lifting upper and lower eyelids occasionally. Get medical attention.

-------------------------------------------------------------------
5. Fire Fighting Measures
Fire:
Flash point: -20C (-4F) CC
Autoignition temperature: 465C (869F)
Flammable limits in air % by volume: lel: 2.5; uel: 12.8
Extremely Flammable Liquid and Vapor! Vapor may cause flash fire.

Explosion:
Above flash point, vapor-air mixtures are explosive within flammable limits noted above. Vapors can
flow along surfaces to distant ignition source and flash back. Contact with strong oxidizers may cause
fire. Sealed containers may rupture when heated. This material may produce a floating fire hazard.
Sensitive to static discharge.

Fire Extinguishing Media:
Dry chemical, alcohol foam or carbon dioxide. Water may be ineffective. Water spray may be used to
keep fire exposed containers cool, dilute spills to nonflammable mixtures, protect personnel attempting to
stop leak and disperse vapors.

Special Information:
In the event of a fire, wear full protective clothing and NIOSH-approved self-contained breathing
apparatus with full facepiece operated in the pressure demand or other positive pressure mode.

------------------------------------------------------
6. Accidental Release Measures
Ventilate area of leak or spill. Remove all sources of ignition. Wear appropriate personal protective
equipment as specified in Section 8. Isolate hazard area. Keep unnecessary and unprotected personnel
from entering. Contain and recover liquid when possible. Use non-sparking tools and equipment. Collect
liquid in an appropriate container or absorb with an inert material (e. g., vermiculite, dry sand, earth), and
place in a chemical waste container. Do not use combustible materials, such as saw dust. Do not flush to
sewer! If a leak or spill has not ignited, use water spray to disperse the vapors, to protect personnel
attempting to stop leak, and to flush spills away from exposures. US Regulations (CERCLA) require
reporting spills and releases to soil, water and air in excess of reportable quantities. The toll free number
for the US Coast Guard National Response Center is (800) 424-8802.

J. T. Baker SOLUSORB(tm) solvent adsorbent is recommended for spills of this product.

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7. Handling and Storage
Protect against physical damage. Store in a cool, dry well-ventilated location, away from any area where
the fire hazard may be acute. Outside or detached storage is preferred. Separate from incompatibles.
Containers should be bonded and grounded for transfers to avoid static sparks. Storage and use areas
should be No Smoking areas. Use non-sparking type tools and equipment, including explosion proof
ventilation. Containers of this material may be hazardous when empty since they retain product residues
(vapors, liquid); observe all warnings and precautions listed for the product.

-------------------------------------------------------------
8. Exposure Controls/Personal Protection
Airborne Exposure Limits:
-OSHA Permissible Exposure Limit (PEL): 1000 ppm (TWA)
-ACGIH Threshold Limit Value (TLV): 500 ppm (TWA), 750 ppm (STEL) A4 - not classifiable as a human carcinogen
Ventilation System:
A system of local and/or general exhaust is recommended to keep employee exposures below the
Airborne Exposure Limits. Local exhaust ventilation is generally preferred because it can control the
emissions of the contaminant at its source, preventing dispersion of it into the general work area. Please
refer to the ACGIH document, Industrial Ventilation, A Manual of Recommended Practices, most recent
edition, for details.
Personal Respirators (NIOSH Approved):
If the exposure limit is exceeded, a half-face organic vapor respirator may be worn for up to ten times the
exposure limit or the maximum use concentration specified by the appropriate regulatory agency or
respirator supplier, whichever is lowest. A full-face piece organic vapor respirator may be worn up to 50
times the exposure limit or the maximum use concentration specified by the appropriate regulatory agency
or respirator supplier, whichever is lowest. For emergencies or instances where the exposure levels are
not known, use a full-face piece positive-pressure, air-supplied respirator. WARNING: Air-purifying
respirators do not protect workers in oxygen-deficient atmospheres.
Skin Protection:
Wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls, as
appropriate, to prevent skin contact.
Eye Protection:
Use chemical safety goggles and/or a full face shield where splashing is possible. Maintain eye wash
fountain and quick-drench facilities in work area.

--------------------------------------------------------------
16. Other Information
NFPA Ratings: Health: 1 Flammability: 3 Reactivity: 0
Label Hazard Warning:
DANGER! EXTREMELY FLAMMABLE LIQUID AND VAPOR. VAPOR MAY CAUSE FLASH
FIRE. HARMFUL IF SWALLOWED OR INHALED. CAUSES IRRITATION TO SKIN, EYES AND
RESPIRATORY TRACT. AFFECTS CENTRAL NERVOUS SYSTEM.
Label Precautions:
Keep away from heat, sparks and flame.
Keep container closed.
Use only with adequate ventilation.
Wash thoroughly after handling.
Avoid breathing vapor.
Avoid contact with eyes, skin and clothing.
Label First Aid:
Aspiration hazard. If swallowed, vomiting may occur spontaneously, but DO NOT INDUCE. If vomiting
occurs, keep head below hips to prevent aspiration into lungs. Never give anything by mouth to an
unconscious person. Call a physician immediately. If inhaled, remove to fresh air. If not breathing, give
artificial respiration. If breathing is difficult, give oxygen. In case of contact, immediately flush eyes or
skin with plenty of water for at least 15 minutes. Remove contaminated clothing and shoes. Wash
clothing before reuse. In all cases, get medical attention.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

The cheap answer is to replace compressor and all seals with 134A compatible material, and use 134A.

Why would you NOT flush it? You have it all apart. Flush it with mineral spirits first and then follow that up with regular a/c system flush to get out the residue. Then blow, blow, blow and make SURE that all flush is out. You can get it out without too much trouble.

Good luck,

Here is a question......what do you use to pump the solvent through it.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

When you pulled a vacuum on the system did you leave the guages on and with the vacuum pump off to see if the vacuum in the system bled off, showing a leak in the system? All the dyes that I'v used were put in when the system was under pressure so you could trace where it came out to find a leak, putting it in under vacuum will just keep it in the system. In any particular system R12 will give you more cooling than 134 but you need to be certified to work with or buy R12. Also R12 is expensive. I would change all seals and the compressor and fill the system with 134. 134 and the charging equipment is available at any auto parts store unlike R12.

__________________
1983 300SD
200000miles

Next question, what do you use to blow it out with? Will an air compressor blow more oils and residue in there, or is that not a problem?

Technically dry nitrogen is called for for blowing out the flush liquid....
You have to ask for dry nitrogen at the gas company when you purchase it...

edit: If you read old manuals they say to use R-11 to flush with.....

Phil, you are new here so you probably did not see the ' AC wars' over the last couple of summers...

To get certified costs about $20 and is an OPEN book test over the internet.

R-12 is about $20 a lb...and the price is coming down... at one time an AC guy around here was charging $60 a lb....

You can get the stuff to deal with R-12 most anyplace that has AC stuff...

These Old Mercedes AC systems seem to have been designed to function well in Germany and Canada. In hot humid climates most people find they need the best ( R-12 ) refrigerant available....

If you are going to change to 134a or suggest others do ... then something else needs to be suggested to take up the natural 20% slack in the efficiency of the molecules compared to R-12.

Your comments are very interesting. I am certified for stationary equipment and work primarily on large commercial systems so its been a long time since I bought R12. If you know the internet site could you let me know. It would be nice to have the automotive certification as well.
Thanks and as always I found out something new today

__________________
1983 300SD
200000miles

whunter,
flushing with acetone is a good idea. I'm well familiar with this stuff, from my previous life, and it has earned my respect -- it's a great solvent (and also forms explosive mixture with air easier than many other organic solvents). As for the compressor: the advice that I've seen most often is to fill the compressor with new oil, rotate X times by hand, dump oil out, repeat. That's what I did. Replacing all seals would be obviously much harder, since I lack the proper tools for a compressor overhaul. What is the risk of running a compressor with some residual amount of old oil left absorbed in the seal? (I don't know if PAG oil was ever in there) If the only risk is the future compressor failure, wouldn't it be worth taking that risk instead of replacing the compressor up front? Since I'm doing my own work, I don't see the benefit of replacing the compressor proactively. I know that a catastrophic compressor failure may send 'black death' dust into the system, but I'm willing to flush it out and install an inline filter if that happens. Since the amount of oil absorbed in the seal is miniscule, I think it would be OK to ignore the moisture that may be present in that oil (and minute amounts of moisture are only a real concern if R12 is used, as I understand, and I hope that any old leftover oil will be long washed out and pumped through the receiver-dryer before I switch to R12). Are there any other risks that I'm not aware of?

Larry,
I did plan on flushing the evaporator initially, but my condenser flushing experience made me doubtful. Plus, I'd have to remove that new expansion valve I just installed... but that's not really a concern. I just feel uneasy about not knowing whether I got all of the liquid out of that evaporator or not. I'm trying to weight the risk of that vs. the risk of having a bit of old (mystery) oil left in the system. Evaporator already got washed with all that UV dye (a few oz) that was circulating in the system for about 5 min...

bonehead,
I got a Mastercool flush gun -- a cylinder with a hose on the bottom and a flush attachment on the end of the hose. Shop air is added on top of the cylinder.

Phil,
The reason 8 applications of UV dye went into the system was me looking for leaks... I did pill vacuum on it first thing, and the system was losing about .5" Hg per hour. UV dye went in, and a couple oz of R-134a. Turned out that the expansion valve was leaking, on the right side (looking from inside the car). I replaced the valve, and at that point the system would hold 29" vacuum for more than a day. There could still be a very slow leak someplace, can't tell with the gauges I got. Thus the plan to put in R-134a and see whether it still leaks. I read all/most of the great R12 vs R-134a threads, and ended up deciding to give R-134a a shot, with the expectation that it'll suck (I'm in Austin, the car is black, and the car is 24 years old, so the evaporator is likely half-blocked on the outside). I got my 609 certification, and am prepared to shell out $30 per can for R12 when the time comes, it's abundantly available on eBay (local auto shops sell it too, but ask closer to $50 a can). I don't like R12 on environmental grounds (I disagree with most people on the forum regarding 'junk science'), but in my case the case for R12 is likely to be too strong, and I'm not an environmental zealot to ignore common sense.

Old Deis,
I do use an air compressor. I know dry nitrogen is the proper way of doing it, but I ain't got any, nor do I have the facilities to store it. I'm counting on the air compressor not to blow much oil into the system. I didn't see any residue after flushing out a few hoses and the condensor, so I don't think external residue is an issue.

Thanks everyone for the advice, I really appreciate it.

I switched to R-134a in my "82 300D. It would not cool acceptably unless the ambient temp was below 85 degrees F. So I'm going back to R-12. I'm planning on a new compressor, exp valve, receiver/dryer and seals. How critical is changing the hoses? I used esther oil, not PAG.

Off topic.... I just noticed that there is some kind of "smart ad" system on this site, maybe you guys noticed this before. Looks like it places an ad at the bottom of the page by what is being mentioned in the posts.

__________________
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

Tango, Did you put in ' barrier' hoses when you changed to R-134a or use the ones which had been used with the R-12 .... or put in new regular R12 hoses ?

Phil, do a search here on the forum for ' 608' or '609' I never can remember which is which... both are certifications.... choose the one you need... you probably have one of them... you can also google for ' epa air condition online test' with those numbers also....
Or just find one of Larry Bible's posts.. he uses his certification in his signature I think...