Is This Air Conditioning Hose A Barrier Hose? - PeachParts Mercedes-Benz Forum

Squiggle Dog · #1 08-07-2015, 08:41 PM

I'm modernizing my 1980 W116 300SD's air conditioning and am replacing all hoses. Except maybe this small one. You see, it will still bolt up as-is and I see no need to change it--except it may not be a "barrier" hose, therefore not compatible with R134a (because the molecules are smaller and may leak through the hose over time).

What do you think? I'll replace the hose if I have to, and don't want to cheapen out, but is it wasted effort and money to replace this hose? I also wonder if I can purchase new hose that is thin enough to fit on the old fitting, anyway. It's the thinnest one that goes to the drier.

leathermang · #2 08-07-2015, 08:52 PM

If that hose was used with R12 many say it will be ok with the R134a. Go ahead and flush it... and use it if you want to.... as you can top off later with 134a since it is NOT a blend... even a completely proper auto ac system loses some refrigerant over time due to a designed leak at the front of the compressor shaft meant to keep the front seal lubed...

97 SL320 · #3 08-07-2015, 10:42 PM

The small one is a liquid line. A few considerations, some years ago ( when R12 was going away ) an automotive trade magazine stated that used R12 hoses tended to absorb oil and "seal" themselves against R134 seepage.

However, given the hose is 35 years old, I'd just replace it and go on from there.

leathermang · #4 08-08-2015, 09:35 AM

Quote:

Originally Posted by 97 SL320

.... an automotive trade magazine stated that used R12 hoses tended to absorb oil and "seal" themselves against R134 seepage.

However, given the hose is 35 years old, I'd just replace it and go on from there.

That is what I was referring to... of course if it is available new as a barrier hose that is the best course of action...

Squiggle Dog · #5 08-08-2015, 11:23 AM

This is the hose that goes from the drier to the expansion valve. Since it's a liquid line, does that mean I don't have to worry about gases leaking through the pores? Though, it sounds like it's probably absorbed enough oil by now to seal it.

I'm thinking I don't want to mess with it, but then again I'd hate to have it leak. But it fits so nicely and I don't know if I can get a new barrier hose that will fit the fitting at the drier, and also onto the expansion valve--and is also the right thickness to still fit on the clamp on the body and the grommet in the firewall.

leathermang · #6 08-08-2015, 11:26 AM

I say leave it on there for the reasons you have stated.

97 SL320 · #7 08-08-2015, 04:16 PM

Quote:

Originally Posted by Squiggle Dog

This is the hose that goes from the drier to the expansion valve. Since it's a liquid line, does that mean I don't have to worry about gases leaking through the pores? Though, it sounds like it's probably absorbed enough oil by now to seal it.

I'm thinking I don't want to mess with it, but then again I'd hate to have it leak. But it fits so nicely and I don't know if I can get a new barrier hose that will fit the fitting at the drier, and also onto the expansion valve--and is also the right thickness to still fit on the clamp on the body and the grommet in the firewall.

The original hose will "work" but for how long? The issue isn't so much that it isn't barrier, it is hose age. The crimped hose end will loose sealing as the rubber shrinks and isn't compressed as tightly.

You can get standard and reduced OD barrier hose if you look around a bit. ( some shops just stock one diameter not wanting to stock 2 or not knowing there are other choices. )

Even though it is a liquid line, the liquid will try to evaporate through the line. Thought as I stated before, the oil from a R12 system will tend to seal the hose.

BillGrissom · #8 08-08-2015, 04:23 PM

The liquid lines on later 1982-85 300D's look better, w/ a smooth plastic outer and perhaps are barrier-type. I have changed all hoses but those on my 84 & 85. If they fit your car, you might get cheap at a junkyard. But, looks like I see a radiator in the background so your filter/drier might be in a totally different location.

mannys9130 · #9 08-08-2015, 04:31 PM

R134a may leak out of non barrier hoses, but it's such a small amount (compared to the front seal leak) that if it's the only hose not replaced you'll probably be fine. If you have to recharge the system every 2 or 3 years, will you be broken up about it? 10 bucks every couple years isn't too bad.

Squiggle Dog · #10 08-08-2015, 04:43 PM

I'm thinking about leaving it on so I don't have to mess with it or anything it's connected to. Then again, if it leaks where it's crimped, then I'm in trouble, and I don't want to find out at the air conditioning shop that it's leaking. I'll do some research and see if I can find barrier hose in the proper size (if I can figure out the inner diameter without cutting the hose). Of course, the car doesn't simply didn't use #6, #8, #10, etc. size hose.

My drier is located in front of the condenser and radiator. I don't know how long a properly sealed air conditioning system should hold a charge (I can never get a definitive answer to this, just "a long time") but I would like this to hold a charge as long as possible.

Squiggle Dog · #11 08-08-2015, 07:21 PM

I just realized that my spare heater box has remnants of the same line in question. I took a look at the cross-section and discovered something interesting; It's not a rubber hose. It has a plastic inner lining wrapped with a layer of cloth, then it is coated with another layer of plastic. So, I doubt there is any chance of leakage in this particular hose. This is assuming it's still clamped nice and tightly at each end. Though, being plastic, it's not as prone to shrinking, so here's hoping. I'm leaning toward leaving this hose as-is and will let the shop determine if it will hold over a 24 hour period.