How often should A/C hoses be replaced? - PeachParts Mercedes-Benz Forum

HuskyMan · #1 06-19-2017, 11:33 AM

I'm starting on my A/C project for the 1984 300DT. I just had the A/C evacuated, the repair shop told me the system was low. I discussed the age of the automobile and A/C hoses with a local mechanic. He feels that at this age, all of the A/C hoses and O rings should be replaced.

Of course this is going to take a LOT of blood, sweat and tears plus $$$$$$$$. Can I get by leaving the old hoses in place? Or would leaving the old A/C hoses in place be an invitation for future A/C system leaks?

ILUVMILS · #2 06-19-2017, 12:08 PM

Add some UV dye to the system. If/when it starts blowing warm again any leaks should be easy to find..........

HuskyMan · #3 06-19-2017, 12:39 PM

I'm thinking with 30 plus year old rubber hoses, probably time to replace. It won't be easy but makes the most sense. The A/C shop people tell me rubber does deteriorate over time.

ah-kay · #4 06-19-2017, 12:58 PM

I wouldn't do it for a number of reasons. Hose by design is porous, depending on molecular size, r12 or r134, so Freon leak is given. How long you think you are going to keep the car? Another 30 years? Very unlikely. You will never get back your investment money, blood or sweat. Just fix any obvious leak and recharge it. Basically, there are other things to break on a 30 years old car. What do you do? Replace them all?

jake12tech · #5 06-19-2017, 12:59 PM

if they leak..

leathermang · #6 06-19-2017, 05:37 PM

Follow your pro's suggestions...
and it would be SILLY to install dye...
for one thing it may contribute to something getting clogged up.. like the TX valve..
AND it WILL NOT SHOW you that the evaporator under the dash is leaking.. and likely not even at high spots in the ac hoses runs...
Suggest you read the AC thread in my signature.

HuskyMan · #7 06-19-2017, 05:55 PM

Is the TX valve the same thing as the expansion valve? If not, where is the TX valve located?

engatwork · #8 06-19-2017, 08:09 PM

Replace them if they leak. Have you priced a new hose manifold assembly from MB lately?

leathermang · #9 06-19-2017, 10:06 PM

Quote:

Originally Posted by HuskyMan

Is the TX valve the same thing as the expansion valve? If not, where is the TX valve located?

TX... short for Thermostatic Expansion valve...

dkr · #10 06-19-2017, 10:38 PM

My recommendation would be to replace them as they start to leak or visually show they may fail soon. I have had that temptation when trying to fix Mercedes things and invariably you will find (especially often with a pro) that they will end up creating new problems due to their inexperience with the system that did not exist before. I know nobody would admit to it, but that happens frequently. Also, many newer products are not made as well as the old OEM ones. I have also had that happen numerous times. It will also be a lot harder to isolate individual problems if you just replace everything at once, but it is often a good deal for the guy selling the work.

Dkr.

ROLLGUY · #11 06-19-2017, 11:06 PM

Quote:

Originally Posted by dkr

My recommendation would be to replace them as they start to leak or visually show they may fail soon. I have had that temptation when trying to fix Mercedes things and invariably you will find (especially often with a pro) that they will end up creating new problems due to their inexperience with the system that did not exist before. I know nobody would admit to it, but that happens frequently. Also, many newer products are not made as well as the old OEM ones. I have also had that happen numerous times. It will also be a lot harder to isolate individual problems if you just replace everything at once, but it is often a good deal for the guy selling the work.

Dkr.

"My recommendation would be to replace them as they start to leak or visually show they may fail soon"
Every time a system is opened, the drier has to be replaced. Every time the system SHOULD be flushed, and new oil put in because the oil leaks out with the refrigerant. The only way to know how much oil is in the system is to start fresh every time. If a hose is replaced, and six months later another hose leaks, you are back where you started. Why is there always time and $ to do a job over, but not enough time and $ to do it right the first time? Like I said, ALL the rubber hoses should be replaced. Even if all the hoses, TXV, Drier and Orings were replaced and the system flushed, vac'd and charged, most R4's are ticking time bombs= it is just not worth it. Also, with the higher pressures from running R134a, the probability of the case slipping on an R4 (very common) is increased. Again, replacing components (hoses) as they exhibit problems (leaks) is a false economy. Do yourself a favor and do it right the first time, you will be glad you did. That is MY recommendation.........Rich

ILUVMILS · #12 06-20-2017, 12:21 PM

Quote:

Originally Posted by leathermang

Follow your pro's suggestions...
and it would be SILLY to install dye...
for one thing it may contribute to something getting clogged up.. like the TX valve..
AND it WILL NOT SHOW you that the evaporator under the dash is leaking.. and likely not even at high spots in the ac hoses runs...
Suggest you read the AC thread in my signature.

I totally disagree. The dye mixes with the refrigerant oil, it won't clog anything. I've been using UV dye for many years and found it to be the single best method of diagnosing A/C leaks, and it will make it quite simple to detect an evaporator leak. I use a UV light to inspect the evaporator drains and have also used a bore-scope when necessary. This method became the standard routine when we realized the 140 S-Class had a problem with premature evaporator failure and we've been using it ever since.

FWIW, I work at an extremely high-volume dealer. We write between 1,300-1,500 repair orders every month and we'll most likely use UV dye on at least 100 cars before the summer is over. If there was an issue using the method described above I think I would be aware of it.

ah-kay · #13 06-20-2017, 12:29 PM

Quote:

Originally Posted by ILUVMILS

I totally disagree. The dye mixes with the refrigerant oil, it won't clog anything. I've been using UV dye for many years and found it to be the single best method of diagnosing A/C leaks, and it will make it quite simple to detect an evaporator leak. I use a UV light to inspect the evaporator drains and have also used a bore-scope when necessary. This method became the standard routine when we realized the 140 S-Class had a problem with premature evaporator failure and we've been using it ever since.

FWIW, I work at an extremely high-volume dealer. We write between 1,300-1,500 repair orders every month and we'll most likely use UV dye on at least 100 cars before the summer is over. If there was an issue using the method described above I think I would be aware of it.

You disagree with our AC guru here with all his signature links? It is unprecedented. Unfortunately I agree with you too.

Mxfrank · #14 06-19-2017, 08:28 PM

Don't buy a factory hose...take your old hoses to a shop that does pneumatic repairs, and have them rebuilt with barrier hose. The result will be perfect, at a fraction of the cost.

ROLLGUY · #15 06-19-2017, 09:54 PM

I have a lot of experience with these systems, and yes they should be replaced, especially if running R134a (smaller molecule than R12). The only exception being the small hose going from the drier into the cabin, and the other small hose from the drier to the condenser (made of a different material). All the other rubber hoses do leak after 25-30 years, especially if running 134a. Having hoses rebuilt properly is also something very few shops do. Either the sleeves need to be split and/or ground off, and new hose (metric) and sleeves crimped on, or the entire rubber section cut off and steel hose barbs welded on, and new hose crimped on. You won't find too many shops willing to do this. That is another reason I make the hoses for the A/C kits I sell. Ditching all the factory hose assemblies, and routing new hoses is less expensive and easier to do. However, this is done with the Sanden retrofit. I have not done an R4 hose remodel. It is my opinion that the R4 is a waste of time and $. However (again), that is not to say that your local A/C shop or hose shop could not make a set of hoses that would replace the factory hoses, but are completely rubber from one end to the other, and routed differently. As others have said, a factory hose assembly is ridiculously priced......Rich