I'll back up again. As these systems age, there is wear internally in the
there can be degradation of the lubricant, seals fail and people put gosh
into the system, etc.
You would hope the lubricant would be pristine and nondegraded, but that
IMO, if you are dealing with a case that might be near "black death", and
the repair to last, you need to flush out the contaminated lubricant
(whether or not
you are upgrading to another refrigerant type).
Some pretty nasty mess can come out of an aging system.
It would seem obvious that you shouldn't reuse oil that has been in
service for a while. That we are even discussing this implies to me that
it is difficult to remove the oil from a system and that in many cases,
old oil is reused. Is this a correct assumption? Why wouldn't one
automatically do this whenever the system is emptied and serviced? Is
this oil expensive or does one use large quantities of the stuff? Thanks.
Now you're cooking. It is not cheap and easy to flush out, so this is only
done if it is needed or indicated. The oil is not particularly expensive,
you do not require much....measured in some ounces, not quarts or gallons.
By the time air conditioning systems fail on a lot of cars, the car is aging
anyway. Refrigerant leaks are the most normal mode of failure, I guess.
When the leaks get so bad that it will not hold a charge over the summer
season, a lot of people dump the car, or even run without AC.
We have a dammitohell GMC Sonoma that ate a compressor last year
with less than 30,000 miles on it. BUT, it is a 2001 model. Compressor
is called a V7, a 7 valve GM design, originally designed to try to get
more out of a system than there is really room for. Costs about $600
to get it going again. I probably WONT even muck with it, but if I
did, I would certainly flush the system, do it right. REASON: The old
compressor failed mechanically...Oil could be full of particles, etc. No
sense in risking an expensive compressor by doing things half way.
Listen, again.. refrigerant can be sucked off and compressed and recovered.
Almost NO refrigerant goes with it. You can reuse the good refrigerant if
have such a system.
YES, you can drain the old compressor. There are instructions how to drain
the oil , but you damn sure dont do it with a vacuum pump.
If the original refrigerant isnt screwed up ("black death"), dont worry
changing out the lubricant. It isnt normally done.
If the system is crudded up, you need to flush the system with solvent,
the filter accumulator drier, pull a vacuum to remove the solvent, and
with lubricant. (This usually means that the compressor is bad and will be
replaced anyway). Then you recharge with coolant.
Now, do you understand the process?
There have been many different colors of the 'security threat rainbow'
regarding how much oil to remove and what is compatible since
conversions came under scrutiny. Even though your question doesn't
involve refrigerant conversions particularly, it's crux does generally
follow the scuttlebutt around conversion dos/donts.
My feelings, after reading everything I can about proper A/C repair and
performaing/monitoring repairs and conversions on many vehicles is
this... It is best to remove as many lines and components as possible
when trying to get rid of contaminated oil or wrong oil for the intended
conversion. I have seen high dollar and normally very reliable
compressors' bearings fail a couple years after conversion from R12 to
R134a. Enough of these failures that I would not want to chance
"saving" someone a couple hundred bucks to convert their system in the
hopes that the compressor will survive. Most mechanics seem to be most
concerned about A) their paycheck and B) getting cars out the door, so
most mechanics will not concern themselves with doing the extra steps
required to get as much oil out as possible. Same goes for most shop
owners. Therefore the overwhelming advice seems to be that adding a
polyester oil during a conversion (guess the amount or add the whole
bottle; who cares, right?!) is a fine alternative to removing as much
oil as possible and adding the correct weight and variety of PAG oil.
It usually doesn't cause a problem. Sometimes it does. My experience
and keen interest in this area has proven, along with much observational
data, that this causes problems with the compressor in some cases. Like
many things, it comes down to risk. I like to take as little risk as
possible. Taking apart lines and blowing refrigerant/oil flush through
as many components as possible (expansion valves and compressors don't
qualify) isn't that hard, and can be easily sold to reasonable customers
whom set aside proper funds to fix their cars.
Back to the basic question... neither evacuating nor vacuuming a system
takes much oil out of the system. Some of the oil is refrigerant-borne,
but the majority of the oil sits in the bottom coils of the heat
exchangers and in the compressor sump area. Modern compressors don't
really hold much oil either, and their respective systems don't call out
for as much oil as older systems. All this means that the quantity and
type of oil is really quite critical in maintaining a long lasting and
fully functional A/C system.
My guess was that most of the oil would be removed along with the
refrigerant. Thanks for giving me the straight dope on this. Please
excuse me if I misunderstand you - it sounds as if you are saying that
the oil should be flushed out and replaced with fresh oil when replacing
the compressor. Is it your experience that reusing the old oil is a
common practice in this type of repair? That is interesting. Sorta like
breaking in a new engine on used motor oil. :-)
It is possible for -some- oil to be removed during the recovery and
evacuation process, it is not unusual to have it happen, it not unusual
to not have it happen.
It depends on where in the system the service ports are located, whether
or not the recovery equipment recovers thru the low side hose, the high
side hose or both, how recently the system was operating and how much
oil is near the service port when the service is performed.
One would consider -why- the compressor is being replaced. If the
compressor mechanically failed then any debris or contamination needs to
be removed via either flushing the components that can be flushed or
replacement of the components that can't be flushed. Flushing will
remove any oil that may be collected in those components and then needs
to be accurately measured and replaced into each of those components.
While there is a volume specification for the total AC system, there is
also a volume specification for each individual component in the system,
the oil needs to be distributed amongst those individual components when
There are mechanics that just flat don't know any better, there are
mechanics who avoid quoting a proper repair because they seem to think
that a half-assed repair (price wise) will scare the customer off.
That's not to say that if one were doing something like replacing an
expansion valve that the entire system needs to be flushed and the oil
replaced with new. In those cases, yes, using "old oil" is perfectly
If the system is old, and has had mechanical problems, I believe it is worth
effort to flush them with solvent until they run clean. Solvent shouldnt
in the compressor, but you can flush the compressor with the lubricant oil
times and drain it.
Of course, I also think the accumulator, filter, drier should be replaced.
You do have to estimate how much new lubricant goes into the system, but
as long as a person is judicious, I havent seen much problem with this.
First of all, a good mechanic/shop is hard to find. Your experience
If you can rule out electrical or mechanical issues and are sure that
the cause is a leak (and therefore low refrigerant), then that leak
should be fixed followed by a recharge. See Interdynamics site on
finding the leaks. There is a limit on how much DIY an owner can do,
but following their steps should help cut down on the costs.
Most (all?) 1994 vehicles came from the factory with R-134a systems.
Unless Toyota was way behind everyone else in converting to R-134a, then
this kind of kit doesn't even apply to your car.Those kits are
half-arsed ways to convert an R-12 system to R-134a, and what they
usually do is destroy an otherwise salvageable AC system completely.
I am not sure I understand your post, Steve. I thought he was just talking
simple R134a recharge kits that we can buy in any FLAPS or WalMart. Some
a gauge on them so that you can top up the refrigerant without having to
have a gauge
set or a refrigerant removal and measuring system.
Some have refrigerant with dyes to help you trace leaks, or even with leak
I dont personally recommend, but have seen others use with occasional
If you can top up a 134a system and get a year or two out of it, great.
These kits are
safe enough for anyone (who is not a total screwup) to use.
If you are talking about those other refrigerant blends which claim to work
in place of R12,
Freeze 12 or whatever they are called, local mechanics tell me they have
used them in old
systems with no problem. I didnt want to go this way with my Reatta (damn GM
so I bought a modern compressor, seals, accum/drier, etc and did it the
correct way. This
is pressing, or beyond, the ability of many DIYers.
A friend, who does not have a vacuum pump, did his own work using a water
pull down the system. It is not as elegant as having a pump, but it worked
like a charm for
him. In essence, you can get down to about the vapor pressure of water with
one of these
which is about 55 mm Hg at 100F (not exactly but about). That is a pressure
over 90% of atmospheric.
A lot depends upon how long you have to keep the car, how much money you
how badly you want to stay cool.
That may indeed be what he meant. But that's not what I thought of when
I heard "kit," to me that usually means a can filled with a mix of
R-134a, a generic stop-leak poo, and a slug of cheap POE oil. I call
those "dead compressor in a can." :-)
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