Is it safe to backflush a parallel flow evaporator core? I ask because I have been told it's almost impossible to clean a parallel flow condenser given its very tiny holes where one can never really get everything out, best to just replace it. But the evaporator is much more difficult to get to than a condenser so can it be flushed safely?
Good question! A modern parallel flow heat exchanger uses several tiny tubes in each cross tube. It is nearly impossible to effectively flush and should be replaced. The method in the video is only for old school, tube and fin designs.
@@BriansGarageUSA Interesting, I’m getting a different answer from another shop stating the evaporator core can indeed be flushed with a good solvent, just not backlashed.
@Mike_44 Well, I work mostly on old cars and am not an A/C guy. So, I recommend doing what your A/C shop suggests. That said, the evap is not easy to replace. So that might be a factor in the decision to attempt flushing it? I'd guess they still intend to replace the condenser, right?
@@BriansGarageUSA I’m doing all the work myself. I feel comfortable wrenching on my cars doing most services, have already swapped two motors so I’m not intimidated by the little a/c work. However, I did not have the knowledge, hence I’ve been doing so much research on the a/c realm. Thank you for help. I will try back flushing the evaporator and the lines. And yes I will also be replacing the condenser and compressor.
Make sure you vacuum from both the low and high side before you charge at least 2 hours. I flushed a Honda out with AC flush only vacuumed the low side found flush was still in the system a month later when I went to check it turned out the oil is mixed with some of the flush now. I vacuumed for 4 hours trying to boil it out of there but not happy about it. I was able to get 40F air but who knows how long it will last. When I removed the high side I could smell that citrus small flush solvent. Acetone probalby better because it will evaporate faster.
That's good advice. I've found that after you have flushed, it's a good idea to blow compressed air thru the tubes to remove any residual liquid. This will also give you an idea of how clean the residual liquid is. If it isn't clear, it isn't clean. Then vacuum for an hour or so. You must get the flush out or it will dilute the oil and the compressor will be starved of lubrication.
When flushing always use a solvent /white spirit that has hydro carbons . If u leave it in a cup it evaporates by itself . Never blow out with compressed air as it will force moisture and small debris into system . Does it matter,, YES moisture degrades into acid also dilutes compressor oil . Micro leaks are caused by this as well . Happens overtime . Remedy blow thru with nitrogen . This lowers the moisture and vacuum pump time will be 2-3 hours [longer the better ] . Blowing with air compressed air deposits moisture and should be evacuated over night
True, probably not a good idea to flush with kerosene.... I fully agree that nitrogen is better than air, but most of us car guys don't have nitrogen sitting around. Also, know that a lot of classic systems have been open to the atmosphere for awhile, so the humidity has already done its thing. You're gonna have to vacuum regardless and you're going to have to use a new drier. Run the vac for an hour and any remaining moisture will get trapped by the desiccant.
Many times once a system has been opened for greater than 48 hrs using vacuum pump over night is enough. A dedicated 3/8----3/4 vacuum line with a 8-10 cfm pump will reduce vacuum time by 50% Using nitrogen to sweep moisture out will reduce vac time as well .
Great tips, thanks! Never thought of using acetone, so that'll be cheaper than buying quarts of flush. When you flushed your evaporator and condenser, were you able to do a good enough job with them still mounted in the vehicle?
You can flush both while still mounted in vehicle. Slip a large hose over the conden/evap tube and direct it into a milk jug to catch the flushed a/c oil and acetone. You may need to flush from both directions (inlet/outlet) until the acetone comes out clear. When vacuum is applied, acetone will evaporate and not leave a residue of itself.
@@BriansGarageUSA Thanks very much for the reply! You've been a big help. That'll save me a lot of work. I'm doing a compressor upgrade kit with a Sanden rotary style compressor from Original Air Group, on my 75 Lemans Sport Coupe. Thanks again!
To be clear: You flush ONLY the condenser and evaporator! NEVER flush the compressor, NOR the hoses. You ALWAYS replace the o-rings on any components that have been disconnected.
Thanks for the video. Are you using high air psi to open the expansion valve. My 65 chevelle valve is hidden deep and I really don’t want to remove it for a flush but I’m not getting even air flow going thru the evaporator. It’s much lower coming out. Feels like a blockage or is it the expansion valve (which is fairly new) not opening? Any thoughts? Thank you
Always remove the expansion valve or orifice tube when flushing. The evaporator normally needs to be flushed from both directions. You don't want any tiny orifices to cause a restriction to debris removal.
Not recommended. Must be something that does not leave a residue once evaporated by vacuum. Ever notice how dirt collects around fuel fillers? That is because the gasoline, once evaporated, leaves an oily film that attracts dirt.
Donna, this really only works on old school cars. Those with tube and fin design. To flush you need to disconnect the evaporator at both ends, then blow the flush through it. Same thing for the condenser. Follow with compressed air. Do not try to flush a drier, accumulator or hose with a muffler.
acetone is all I've ever used....super fast evap rate helps also....
I'm going on 18 years when I swapped from r12 to 134a, didn't change nothing, still going strong.
That's great. Here in Oklahoma, the compressors run very hard in the Summer. If things aren't perfect, it'll smoke the compressor.
We usually use r141B for flushing ;but acetone should also be fine.
Is it safe to backflush a parallel flow evaporator core? I ask because I have been told it's almost impossible to clean a parallel flow condenser given its very tiny holes where one can never really get everything out, best to just replace it. But the evaporator is much more difficult to get to than a condenser so can it be flushed safely?
Good question! A modern parallel flow heat exchanger uses several tiny tubes in each cross tube. It is nearly impossible to effectively flush and should be replaced. The method in the video is only for old school, tube and fin designs.
@@BriansGarageUSA Interesting, I’m getting a different answer from another shop stating the evaporator core can indeed be flushed with a good solvent, just not backlashed.
@Mike_44
Well, I work mostly on old cars and am not an A/C guy. So, I recommend doing what your A/C shop suggests.
That said, the evap is not easy to replace. So that might be a factor in the decision to attempt flushing it? I'd guess they still intend to replace the condenser, right?
@@BriansGarageUSA I’m doing all the work myself. I feel comfortable wrenching on my cars doing most services, have already swapped two motors so I’m not intimidated by the little a/c work. However, I did not have the knowledge, hence I’ve been doing so much research on the a/c realm. Thank you for help. I will try back flushing the evaporator and the lines. And yes I will also be replacing the condenser and compressor.
Make sure you vacuum from both the low and high side before you charge at least 2 hours. I flushed a Honda out with AC flush only vacuumed the low side found flush was still in the system a month later when I went to check it turned out the oil is mixed with some of the flush now. I vacuumed for 4 hours trying to boil it out of there but not happy about it. I was able to get 40F air but who knows how long it will last. When I removed the high side I could smell that citrus small flush solvent. Acetone probalby better because it will evaporate faster.
That's good advice. I've found that after you have flushed, it's a good idea to blow compressed air thru the tubes to remove any residual liquid. This will also give you an idea of how clean the residual liquid is. If it isn't clear, it isn't clean. Then vacuum for an hour or so. You must get the flush out or it will dilute the oil and the compressor will be starved of lubrication.
I like your video very much. Is acetone one recommended by flush tube, condensor manufacturer,etc. DId some reliable source say this?
When flushing always use a solvent /white spirit that has hydro carbons . If u leave it in a cup it evaporates by itself . Never blow out with compressed air as it will force moisture and small debris into system . Does it matter,, YES moisture degrades into acid also dilutes compressor oil . Micro leaks are caused by this as well . Happens overtime .
Remedy blow thru with nitrogen . This lowers the moisture and vacuum pump time will be 2-3 hours [longer the better ] . Blowing with air compressed air deposits moisture and should be evacuated over night
True, probably not a good idea to flush with kerosene....
I fully agree that nitrogen is better than air, but most of us car guys don't have nitrogen sitting around. Also, know that a lot of classic systems have been open to the atmosphere for awhile, so the humidity has already done its thing. You're gonna have to vacuum regardless and you're going to have to use a new drier. Run the vac for an hour and any remaining moisture will get trapped by the desiccant.
Many times once a system has been opened for greater than 48 hrs using vacuum pump over night is enough. A dedicated 3/8----3/4 vacuum line with a 8-10 cfm pump will reduce vacuum time by 50% Using nitrogen to sweep moisture out will reduce vac time as well .
Great tips, thanks! Never thought of using acetone, so that'll be cheaper than buying quarts of flush. When you flushed your evaporator and condenser, were you able to do a good enough job with them still mounted in the vehicle?
You can flush both while still mounted in vehicle. Slip a large hose over the conden/evap tube and direct it into a milk jug to catch the flushed a/c oil and acetone. You may need to flush from both directions (inlet/outlet) until the acetone comes out clear. When vacuum is applied, acetone will evaporate and not leave a residue of itself.
@@BriansGarageUSA Thanks very much for the reply! You've been a big help. That'll save me a lot of work. I'm doing a compressor upgrade kit with a Sanden rotary style compressor from Original Air Group, on my 75 Lemans Sport Coupe. Thanks again!
I would thing acetone would dissolve any o-ring seals and ruin the compressor and evaporator.. never tried it tho..
To be clear:
You flush ONLY the condenser and evaporator! NEVER flush the compressor, NOR the hoses. You ALWAYS replace the o-rings on any components that have been disconnected.
Thanks for the video. Are you using high air psi to open the expansion valve. My 65 chevelle valve is hidden deep and I really don’t want to remove it for a flush but I’m not getting even air flow going thru the evaporator. It’s much lower coming out. Feels like a blockage or is it the expansion valve (which is fairly new) not opening? Any thoughts? Thank you
Always remove the expansion valve or orifice tube when flushing. The evaporator normally needs to be flushed from both directions. You don't want any tiny orifices to cause a restriction to debris removal.
No demo? Really
👍
How about using petrol instead of Acetone?
Not recommended. Must be something that does not leave a residue once evaporated by vacuum. Ever notice how dirt collects around fuel fillers? That is because the gasoline, once evaporated, leaves an oily film that attracts dirt.
Thanks man!
No problem!
Says AC flush but doesn't do anything but talk 😡
Donna, this really only works on old school cars. Those with tube and fin design. To flush you need to disconnect the evaporator at both ends, then blow the flush through it. Same thing for the condenser. Follow with compressed air. Do not try to flush a drier, accumulator or hose with a muffler.