Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 06-16-2016, 07:03 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,245
Quote:
Originally Posted by vstech View Post
I'll start the ball rolling.

to properly test a refrigeration (A/C) system for leaks you need PRESSURE! it must be in the form of a gas. NO liquid can be present or it invalidates the test.
Standard test gas is Dry nitrogen. CO2 can be used as can any gaseous refrigerant, but refrigerants are NOT legal to vent, so it's not a good idea to use them unless you have recycling equipment.

testing for leaks with vacuum is a ridiculous plan. I know MANY shops and individuals think it's a good way to test for leaks. It is NOT!
on a rigid piped system (home a/c or refrigerators etc) vacuum can and is used to test for leaks as well as moisture presence... but a DIGITAL micron gauge is required for the test.
mobile refrigeration with flex lines, and semi hermetic compressors with a shaft driven compressor simply cannot reliably be tested with vacuum. the rubber will mask a vacuum leak test, and the crank seals will vent moisture into the compressor, and the dryer in short order...
There is liquid oil throughout the AC system components. So the system must be disassembled and flushed of the oil first, then put back together, before doing the pressure test? Otherwise the 200 psi nitrogen/ R22 test is invalid?
__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
Reply With Quote
  #2  
Old 06-16-2016, 09:39 PM
Registered User
 
Join Date: Mar 2009
Location: San Diego
Posts: 3,579
Quote:
Originally Posted by funola View Post
There is liquid oil throughout the AC system components. So the system must be disassembled and flushed of the oil first, then put back together, before doing the pressure test? Otherwise the 200 psi nitrogen/ R22 test is invalid?
No. If it is a must then all ac shop will be out of business or they charge you exorbitant amount of money.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
Reply With Quote
  #3  
Old 06-16-2016, 10:27 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,245
Quote:
Originally Posted by ah-kay View Post
No. If it is a must then all ac shop will be out of business or they charge you exorbitant amount of money.
AC shops will not go out of business because they don't use nitrogen/ R22 pressure test. I called 6 local shops today and ask if they do such a test and none of them has the equipment for it. 2 of the shops specialize in AC and radiators and they all use either dye or vacuum to find leaks. There's another AC thread where another forum member could not find a shop that uses nitrogen/R22.

It seems this is the only forum that says nitrogen/R22 at 200 psi is the only way to find leaks. But if the test is invalid when there is liquid oil in the system, the test is not very practical is it?
__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
Reply With Quote
  #4  
Old 06-16-2016, 10:51 PM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,290
Quote:
Originally Posted by funola View Post
AC shops will not go out of business because they don't use nitrogen/ R22 pressure test. I called 6 local shops today and ask if they do such a test and none of them has the equipment for it. 2 of the shops specialize in AC and radiators and they all use either dye or vacuum to find leaks. There's another AC thread where another forum member could not find a shop that uses nitrogen/R22.

It seems this is the only forum that says nitrogen/R22 at 200 psi is the only way to find leaks. But if the test is invalid when there is liquid oil in the system, the test is not very practical is it?
You can get an AC system to work for a year without doing a really good job.... I do not know of any R22 / nitrogen shops either.. I volunteered to bring my nitrogen tank so my local shop could use it .. you may be underestimating the thickness and lack of pride some of these people show in their work... they do not read... they just do what they learned to do in the shop... but a customer who knows they did a shoddy job will not likely come back after a year to have them fix it again...

The MB AC FSM shows a tool for injecting oil into the system while the system is still under pressure.. meaning after you have installed the refrigerant.... If that is what Vstech was meaning ... I am not sure what his statement might have been in response to....
Reply With Quote
  #5  
Old 06-17-2016, 12:41 AM
Registered User
 
Join Date: Mar 2009
Location: San Diego
Posts: 3,579
Quote:
Originally Posted by funola View Post
AC shops will not go out of business because they don't use nitrogen/ R22 pressure test. I called 6 local shops today and ask if they do such a test and none of them has the equipment for it. 2 of the shops specialize in AC and radiators and they all use either dye or vacuum to find leaks. There's another AC thread where another forum member could not find a shop that uses nitrogen/R22.

It seems this is the only forum that says nitrogen/R22 at 200 psi is the only way to find leaks. But if the test is invalid when there is liquid oil in the system, the test is not very practical is it?
No, let me rephrase it. This is the only forum with self proclaimed A/C guru who uses Nitrogen/R22 to pressurize the system to 250+ psi. Most of them pull vacuum or just pressurized with compressed air, then vacuum. I seriously doubt it is a good ides to pressurize it to 250+ psi. The high side of A/C system is spec'ed to 300+ psi. I am not sure whether the low side is spec'ed that high. Some hoses doesn't look like pneumatic grade.

You can pressurize the system with oil in it. Liquid is in-compressible, so the oil just sit there and acts like a thicker tube. As I have said before, A/C is very simple, important thing is to take safety precaution. I am not an A/C professional but I know enough to DIY or do R134a conversion.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
Reply With Quote
  #6  
Old 04-15-2011, 11:33 PM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,996
Quote:
What are the best sources for dry nitrogen/R22?
craigslist.

Quote:
any HVAC supplier will sell you a tank for 200ish, and a regulator for 50 ish... craigslist sells tanks with regulators for 50ish..
you can also use CO2 which comes in a smaller lighter tank with a MUCH larger useage at lowes or home depot for 90ish. you would then have to rig an air chuck adapter to hook up your manifold to.
you can also use one of those helium baloon tanks, but one 30.00 tank will just about be empty after one use.

Quote:
Originally Posted by zeke View Post
What are the best sources for dry nitrogen/R22?
Your local Welding supply shop.
Ebay for R22 in 15 oz can...
which I am still trying to figure a way to split three ways evenly... I guess an accurate scale would be good too.. just like you would do the refrigerant if you used a big tank to install it...
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Last edited by vstech; 06-06-2011 at 06:12 PM.
Reply With Quote
  #7  
Old 04-15-2011, 11:42 PM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,290
Good start..
Except R22 in the amount of FOUR Ounces... put into an automotive system with nitrogen to pressurize it.. IS LEGAL.... per EPA... so that people can test under pressure..as you recommend...
the reason pressure is needed is so that the orings involved are in their WORKING position..
not being pulled IN by vacuum... when they need to hole being pushed out by pressure...
Reply With Quote
  #8  
Old 04-16-2011, 12:01 AM
Registered User
 
Join Date: Jun 2008
Location: Orlando, FL
Posts: 1,269
So what tools are necessary to pressurize the system with something such as nitrogen or co2? I have always done the vac-down method, but that's because I was none the wiser...
Reply With Quote
  #9  
Old 04-16-2011, 12:08 AM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,290
You were doing the correct thing ... that is for getting the moisture out...so that acid does not form from the mixing of moisture and the oil in the system... causing flakes to come off the inside and plug up tiny holes ..like in the TXValve.
We are just saying that THEN... to test for leaks... you need pressure..
you can use a normal set of hoses and gauges... there are regulators which fit on the nitrogen tanks just like Oxy or Acet...
then that hooks to your AC gauges and you open the proper valves...
I have a nitrogen tank and gauges...will post pics... but can not find my dang camera... been missing for four days...
Reply With Quote
  #10  
Old 04-16-2011, 09:25 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,996
Quote:
Originally Posted by francotirador View Post
Hello: I have a 1990 300SE and I would like to revert the system to R12. It was converted to R134 by the original owner. I read a long thread posted hereon where the original question was essentialy "how do you convert back to R12 from R134?" That question was posed a few times during the thread and it was really not answered.

So, please tell me, how do you convert a system from R134 to R12? The compressor I have is good for both types of refrigerant. I understand a different oil must be used. I know the drier has to be changed and the correct amount of R12 must be introduced into the closed system. I imagine the Schrader valve fittings must also be changed.

However, what I don't know is if there any other fittings, seals, hoses...that must be changed for use with R12?

If you would post the details of the R134 to R12 conversion I, and many others, would greatly appreciate it.

Thank you.

Great question.
several levels of answers can be dependent on what the 134 "conversion" entailed.
first, the Oil in the system. if you do not know what kind was used, it's best to replace the compressor, the expansion valve, and the compressor manifold, with the dryer and flush the remaining coils with oil/refrigerant flush, then add the correct amount of mineral oil to the system, pulling a hard vacuum, then weighing in the correct volume of R12.
this is the BEST method to convert back to 12.
PAG oil is not compatible with R12, Ester is. if you don't know, it's best to assume PAG was used, and do it right. however, since doing it wrong will destroy your compressor, requiring you do do all that stuff, if the wrong oil is used, and will not if Ester is in there, simply evacuating the refrigerant, measuring how much oil came out with it, and replacing that with the same amount of ester oil, then flowing the weighed amount of R12 will put the system back to R12. however you will still have the 134 fittings on the system... if you try to remove them, you can damage the lines (don't ask how I know this) this is why it's needed to replace the compressor manifold.
then lastly the 134 sticker needs to be removed.
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Last edited by vstech; 06-06-2011 at 06:06 PM.
Reply With Quote
  #11  
Old 04-16-2011, 03:52 PM
Registered User
 
Join Date: Jul 2010
Location: Southern FL
Posts: 227
Quote:
Originally Posted by vstech View Post
Great question.
several levels of answers can be dependent on what the 134 "conversion" entailed.
first, the Oil in the system. if you do not know what kind was used, it's best to replace the compressor, the expansion valve, and the compressor manifold, with the dryer and flush the remaining coils with oil/refrigerant flush, then add the correct amount of mineral oil to the system, pulling a hard vacuum, then weighing in the correct volume of R12.
this is the BEST method to convert back to 12.
PAG oil is not compatible with R12, Ester is. if you don't know, it's best to assume PAG was used, and do it right. however, since doing it wrong will destroy your compressor, requiring you do do all that stuff, if the wrong oil is used, and will not if Ester is in there, simply evacuating the refrigerant, measuring how much oil came out with it, and replacing that with the same amount of ester oil, then flowing the weighed amount of R12 will put the system back to R12. however you will still have the 134 fittings on the system... if you try to remove them, you can damage the lines (don't ask how I know this) this is why it's needed to replace the compressor manifold.
then lastly the 134 sticker needs to be removed.
Thank you for your detailed response. I appreciate it.

When I last evacuated and charged the system I used ester oil. I don't know what the car originally came with. I do plan on changing the compressor. However, if I could run the system on R12 for a while before changing the compressor and any lines, that would suit me nicely.

Are you saying that I cannot swap the R134 fittings for R12 fittings without damaging the lines? Or, are you saying I must be careful or I will damage them?
Reply With Quote
  #12  
Old 04-16-2011, 10:16 AM
Yak Yak is offline
Registered User
 
Join Date: Aug 2009
Location: San Antonio, TX
Posts: 1,711
Removing R-12-to-134a-adapter fittings is primarily dependent on the original conversion. Since these kits are sold in any autoshop they may/may not have been "properly".

Some may have been spot-brazed in place, others are simply screwed on. Some kits appear to have thread-locker on the new fittings while others don't. Some conversions only changed the low-pressure/blue/"fill-port" on the top-front of the engine to a 134a fitting and left the original R-12 high-pressure/red/"service-port" alone.

Modifications to fittings may affect the integrity of the schrader valve directly beneath it. The valves should have caps with O-rings in them.

Before attempting any conversion/de-conversion you really need to inspect the whole system and be prepared to invest in new components where necessary. This includes the proper operation of the heater and the cooling system of the car.

Some new components (e.g. R-4 compressors) may not honor the warranty if used in an R-12 "de-conversion". You need to decide if the warranty vs. performance trade-off is worth it when selecting what refrigerant you use.

The A/C lines and fittings, even though they're on an otherwise metric car, are SAE sized. Having the right tools is also very important.

You really cannot assume anything when you're working on the A/C.
Reply With Quote
  #13  
Old 09-03-2018, 12:41 PM
JHZR2's Avatar
Registered User
 
Join Date: Jan 2002
Location: New Jersey
Posts: 5,427
Quote:
Originally Posted by Yak View Post

The A/C lines and fittings, even though they're on an otherwise metric car, are SAE sized. Having the right tools is also very important.

You really cannot assume anything when you're working on the A/C.

I’m primarily concerned about the W123, but other vehicles are relevant in this thread.

Is this everybodys’ observation on all Daimler vehicles of general interest here (115/123/124/126) that may have run R12?

I will have my system open and therefore will plan to replace all o-rings with new green ones and the appropriate nylog for R-12. But want to be double sure that I’m using the right sized ones. I assume the fittings and o-ring sizes are associated with each other?
__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)
Reply With Quote
  #14  
Old 04-16-2011, 10:32 AM
Registered User
 
Join Date: Sep 2001
Location: central Texas
Posts: 17,290
"Having the right tools is also very important."--Yak
When dealing with AC lines.... it is always suggested that two wrenches be used.. and often the proper wrenches will be what is called ' Line wrenches " or "?"... these are open end wrenches which wrap more than 180 degrees around the nut. But are still large enough on the open side to fit over the tube next to the nut or fitting... so they can be used in tight places to protect the line from being crunched...which is the most important place to exercise caution because having to replace the line in a tight place is really a chore.
Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 10:44 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page