A/C fittings threads - PeachParts Mercedes-Benz Forum

cbjukraine · #1 05-09-2014, 02:46 AM

I couldn't find anything related to this in a search...

What kind of threads do all of the hose fittings in the A/C system of an 84 300D have? Parallel, tapered, NPT, standard... I can't keep them all straight.

I want to get plugs and adapters to block off the various components (condenser, evaporator, etc...) and leak test them with pressure. I've got a leak somewhere and I want to get it fixed before I upgrade to a Sanden compressor. I'm done with that crap design known as the R4 and its insidious stepped ports.

Thanks

rscurtis · #2 05-09-2014, 10:13 AM

Pressurize the system with nitrogen and some R22 and use a leak detector- you'll find all the leaks.

cbjukraine · #3 05-09-2014, 10:42 AM

Why R22? Doesn't someone looking to buy need an EPA cert? Could I use R134 instead? Or is it bad to mix them since I eventually plan to use R12...? (R12 that my licensed mechanic will handle...)

ROLLGUY · #4 05-09-2014, 11:35 AM

The easiest thing to do is to take the car to your local A/C shop to have it leak tested. One method is to use nitrogen to pressurize the system and check for leaks with a soap and water solution in a spray bottle. I personally use all 3 testing methods to find leaks: ultra-violet light and glasses, soap solution, and a halogen leak detector ("sniffer"). Again, your A/C shop should have and use all three as well. All the fittings are Oring type fittings ranging from #6 (drier) up to #12 (connection on the left side of the hard pipe). It is best to test with the system intact, rather than testing separate components. Chances are your leak is in or around the compressor. That is the usual suspect. You may be better off replacing the compressor and hoses and then check for leaks (standard procedure before a vac and charge)....Rich

cbjukraine · #5 05-09-2014, 12:01 PM

I hear what you're saying, Rich, but that means I need to order the Sanden bracket from you first!

I'm just very skeptical, as I've already had to replace the evaporator on this car. That was fun... turned out there was a pinhole in one of the coil's u-bends.

ROLLGUY · #6 05-09-2014, 12:21 PM

Quote:

Originally Posted by cbjukraine

I hear what you're saying, Rich, but that means I need to order the Sanden bracket from you first!

I'm just very skeptical, as I've already had to replace the evaporator on this car. That was fun... turned out there was a pinhole in one of the coil's u-bends.

Not necessarily. Just find someone that can pressurize the system (dry gas or refrigerant) and leak check with one or all three methods. If the ONLY leak is in the compressor or any of the hoses/fittings that will be removed with the Sanden retrofit, then you know what you have to do. If you find a leak somewhere else (condenser, evaporator, hose connection etc), then you also know what you have to do. If your leak is slow, then it is harder to find. If you have dye in the system, you can use the glasses and light to view the condensate drain (above trans). If there is a leak in the evaporator, you will see green in the condensate. This is the best way to check the evaporator. You can soap the connections around the TXV and hoses, and also the condenser. I usually have my A/C shop check for leaks before charging, but I have my own gas bottle (CO2) and hose assembly that I use to check for leaks. My bro' has an R4 system in his 300D that works for a couple months, and leaks out before the hot season is done. I have tried every method several times to find the leak, with no avail. Good luck to you with yours...Rich

cbjukraine · #7 05-09-2014, 12:33 PM

If there were another leak in the evaporator, I would drive the car off a cliff or into a lake...

cbjukraine · #8 05-09-2014, 01:20 PM

Rich, I have a nitrogen cylinder right now with about 1500 psi still in it. Got the regulator too. Do you think it would be wise to go buy a small bottle of r134 and shoot a little in there? I could pick up the cheap Harbor Freight sniffer and check that way. I've tried the soapy water test with no results.

I intend to use R12 eventually, so I don't really want to re-flush the system if the R134 will contaminate the R12 mineral oil.

The last time the compressor (R4) was on the car a few days ago, I pressurized to 200 psi and it leaked down to 160 psi overnight. Not sure if that qualifies as a slow leak, but it seems like a big one to me.

The back story here is that the A/C was working great (33-34* vent temps in high 90s weather) in Summer 2012 by installing a new Compressorworks R4, flushing, and charging with R12/Mineral oil. But then I had to put the car in storage for 15 months, and when I came back to get it, the R12 was all gone.

Phillytwotank · #9 05-09-2014, 02:00 PM

have you checked the shrader valves?

ROLLGUY · #10 05-09-2014, 02:16 PM

Quote:

Originally Posted by cbjukraine

Rich, I have a nitrogen cylinder right now with about 1500 psi still in it. Got the regulator too. Do you think it would be wise to go buy a small bottle of r134 and shoot a little in there? I could pick up the cheap Harbor Freight sniffer and check that way. I've tried the soapy water test with no results.

I intend to use R12 eventually, so I don't really want to re-flush the system if the R134 will contaminate the R12 mineral oil.

The last time the compressor (R4) was on the car a few days ago, I pressurized to 200 psi and it leaked down to 160 psi overnight. Not sure if that qualifies as a slow leak, but it seems like a big one to me.

The back story here is that the A/C was working great (33-34* vent temps in high 90s weather) in Summer 2012 by installing a new Compressorworks R4, flushing, and charging with R12/Mineral oil. But then I had to put the car in storage for 15 months, and when I came back to get it, the R12 was all gone.

If the system is not used, it will definitely leak out after sitting that long. If you have the compressor off the car now, the only thing you could do is to make some kind of adapter hose to test the system without the compressor in place (yes I think that is what you originally suggested). If you will be going with the Sanden, the only factory hoses you will need are the two going into the cabin (little one connected to the drier, and big one connected to the low side hard pipe). You would need to make a hose that has a #12 male Oring on one end, and a #10 female Oring on the other with some kind of port in the middle. That way, you would only be testing the components that would remain as part of the new system. The other option would be that which I suggested earlier= install all the new components and then leak test. If you still have a bad evaporator or condenser, either way of testing should reveal it.

ROLLGUY · #11 05-09-2014, 02:26 PM

Quote:

Originally Posted by cbjukraine

Rich, I have a nitrogen cylinder right now with about 1500 psi still in it. Got the regulator too. Do you think it would be wise to go buy a small bottle of r134 and shoot a little in there? I could pick up the cheap Harbor Freight sniffer and check that way. I've tried the soapy water test with no results.

I intend to use R12 eventually, so I don't really want to re-flush the system if the R134 will contaminate the R12 mineral oil.

The last time the compressor (R4) was on the car a few days ago, I pressurized to 200 psi and it leaked down to 160 psi overnight. Not sure if that qualifies as a slow leak, but it seems like a big one to me.

The back story here is that the A/C was working great (33-34* vent temps in high 90s weather) in Summer 2012 by installing a new Compressorworks R4, flushing, and charging with R12/Mineral oil. But then I had to put the car in storage for 15 months, and when I came back to get it, the R12 was all gone.

I am not sure about contaminating the oil, but you would not want to mix refrigerant if you are going to recycle (recover) it. If you want to use a sniffer for testing, use R22 as suggested previously (venting is allowed by law). You don't want to use R12, as it will be wasted. If you had dye in the system previously and have an evaporator leak, you should be able to see evidence of it in the condensate drain, or on the trans.

97 SL320 · #12 05-09-2014, 04:11 PM

Nitrogen is good to check for gross leaks.

It doesn't take much freon to get the system up to max / near max _static_ pressure. In a fully charged system there is liquid freon lurking around, if you are leak testing there is no need to fully charge the system.

The compressor shaft seal might have a slight leak from sitting, turning it might help.

cbjukraine · #13 05-09-2014, 04:23 PM

Where can one buy small quantities of R22?

rscurtis · #14 05-09-2014, 04:40 PM

I don't know if the small cans can still be found, but it's still used in HVAC systems. The reason for using 22 is that it's compatible with R12 and easier on the environment when it leaks out. I wouldn't contaminate a future R12 system (which is the best way to go) with 134.