Barrier vs. R-12
There are three separate issues discussed using the same photos, so you get to see them over and over here.Kirby Palm's 1983 Jaguar XJ-S came with this freon hose:
The first issue is the hose itself. That is an R-12 hose. How
can you tell? Because it has cloth on the outside. Reportedly
later R-12 hoses were color coded red, but still cloth. Those hoses
are no longer manufactured, but there is equivalent hose commonly available
that is black; they're just not listed as intended for freon.
By the way, that hose has braided metal under the cloth. You
won't be cutting this hose with a razor knife.
Barrier hoses have smooth rubber surfaces -- like this one:
This hose actually says "Barrier" right on it, although it's not visible
in this picture.
Most mechanics now agree that it's not really necessary to convert to barrier
hoses when converting from R-12 to R-134a. Supposedly this is because
the mineral oil that was used in the R-12 system has permeated the inside
surface of the hose and sealed it so R-134a won't leak through it. Even
if it does leak, it's only a few ounces a year, so it's arguably cheaper
to just top it off occasionally than fiddle with hose upgrades. OTOH,
it's really not very expensive to haul the three large hoses from the XJ-S
into an industrial hose shop and have them build a new set to fit.
Second issue: The connections between the hose and the end fittings
are different. That barrier hose above is obviously crimped onto the
fitting. The fitting itself is aluminum, but the crimp sleeve is steel.
There is actually a color code used here; this is a crimp for a 5/8"
line, and it has that brass tint to it. The crimp sleeve for a 1/2"
line -- such as the high pressure line on this car -- has silver-colored
The connections on the R-12 line are a whole different animal:
This is a threaded compression connection. The tube itself is steel, and hidden within this assembly is a fine thread and then a tapered end. That aluminum collar has a mating fine thread within the end nearest the small hex, and a big coarse left-hand thread that digs into the outer sheath of the hose itself.
The way to get that thing apart is to clamp the hose itself down in a vice
and use a wrench to hold that small hex still. Then with a big wrench
turn that aluminum collar in the direction that would unscrew it from the
fine thread on the steel tube. Since the coarse thread gripping the
hose itself is left-hand, turning that direction also unscrews the collar
off the outside of the hose. As you turn that collar, it will pull the
tapered end of the steel tube out of the hose. You'll end up with parts
that look like this:
Of course, there's no good reason to take it apart. This coupling
cannot be used with barrier hose. The only way to reuse this fitting
with barrier hoses is to saw off the fitting itself and braze on a barb suitable
for crimping a hose to. Since the fitting end is a standard fitting,
that isn't worth doing; just install a new standard fitting. They're
usually aluminum, so you save a little weight and get a part that won't rust.
Third issue: When having these hoses rebuilt with barrier hoses,
Palm had the shop change the configuration of the hose that goes from the
firewall to the fuel cooler. The original hose had a 45° fitting
on both ends. Palm had the new hose made with a straight end at the
fuel cooler end, and also made the overall length of the hose about 1-1/4"
shorter. Here are two pix of how it fits:
This looks like it was made to fit -- as opposed to the way the original hose fit, which was all twisted and crammed in there.
There is a second advantage to putting a straight end at one end, and that
is that the shop building the hose doesn't have to worry about angles when
assembling. With a 45° at both ends, the fittings have to be aligned
properly when crimped; it's hard to twist a freon hose, and the fittings
won't slip under the crimps either. With one end straight, none of
You can also read all about keeping that
hose from fouling the throttle linkage.
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