Automotive Air Conditioning Information Forum

hi guys, i have an aftermarket o-ring kit, part # MT2506 for my 03 dodge caravan with 3.3 v6. according to multiple sellers this should be correct for my application. of course it has a bunch of o-rings of various sizes, problem is i can't tell which one is which. the old o-rings are to deformed to be useful for comparison and some of the rings in the package are so close in size i have to use a digital caliper to tell them apart. in some cases two slightly different size rings seem to fit but they both can't be right. is there any way to tell? thanks.

With a kit like that, the best you can do is choose an o-ring that looks like it will fit, try it on the male fitting, then check whether it fits into the female fitting using light finger pressure. If so, you've probably found a good match. Just before installation, lubricate the o-ring with a small amount of Nylog Blue to ensure a leak-free seal.

hi john, except for the nylog, that's what i did. hopefully, the o-rings i picked will work. going to my flaps tomorrow for a pump to pull a vacuum on the system. that should let me know if i have any leaks. never heard of nylog. i'll give it a try if i find any leaks. how hard is it to disassemble the system after using it? is it difficult to clean up? thanks, frank

You may end up getting it on line.
There will be no problem with disassembly

3154tm wrote: ↑Thu Jun 27, 2024 6:21 pm except for the nylog, that's what i did. hopefully, the o-rings i picked will work. going to my flaps tomorrow for a pump to pull a vacuum on the system. that should let me know if i have any leaks.

If your FlaPS loans or rents you a vacuum pump, be aware that those units are often abused, and the oil is very rarely, if ever, changed. Suggest that you change the old oil before trying to use the pump. Special vacuum pump oil should be used—and not anything else—to achieve the best possible vacuum. If you're located at the Redneck Riviera, you'll be near sea level. At that elevation, you should be able to achieve a vacuum of 29.92 inHg or 500 microns. If not, try to get a different pump that will achieve such a deep vacuum.

Be aware that a system can often hold a vacuum well but might leak under pressure, especially on the high side.

3154tm wrote: ↑Thu Jun 27, 2024 6:21 pm never heard of nylog. i'll give it a try if i find any leaks. how hard is it to disassemble the system after using it? is it difficult to clean up? thanks,

Nylog Blue is made of very thick double-end-capped PAG oil that will facilitate disassembly later should you need to do so, as tbirdtbird said. It's no more difficult to clean up than regular PAG oil. It's used on o-rings and threaded joints and never sets up or hardens.

john, your absolutely right. the first one i got from autozone was clapped out, low on oil and wouldn't pull more than about 27"hg. got lucky with the second one from o'reilly's, it was new in box and pulled 29"hg plus. the system was still holding that vacuum after 3 hours so i'm going to move on to trying to charge it. thanks for the advice.

Today's MVAC systems are very sensitive to the correct refrigerant amount. So be sure to weigh-in the R-134a using an accurate refrigerant scale for optimum system performance.

Ensure that you purge the yellow hose before charging so that you don't drive any unwanted air and moisture into the system. If you use the small 12-ounce cans, make sure that they contain only pure refrigerant—no sealer or other additives—with the exception of yellow-green fluorescent dye, which is okay for leak testing purposes.

Keep each can upright to charge refrigerant gas only into the low side. Never invert the cans to charge liquid into the low side. And keep the high-side handwheel on your Manifold Gauge Set fully closed.

The three specifications that I have for your Caravan are as follows:
With front A/C only, single or dual zone — 31 ounces net weight of R-134a, and 5.0 fluid ounces of PAG-46.
With front A/C only, three zones — 43 ounces net weight of R-134a, and 6.4 fluid ounces of PAG-46.
With front and rear A/C, single or dual zone — 31 ounces net weight of R-134a, and 6.4 fluid ounces of PAG-46.

thanks john, that's great advice. since, except for the pag oil, the system is empty i'm going to try and have it charged by weight. the folks up the street have one of those programable machines and have quoted $100 to do it. all things considered it seems worth it. if i use the little 12 oz cans i'm sure i'd end up with a lot of air and either to much or to little freon. if i had access to a good scale and a large container of freon i'd give it a shot. thanks again, frank
ps. i'll take those specs with me when i go.

Sounds like a great idea having them do the job by using a professional R/R/R machine (Recover/Recycle/Recharge).

As for the small 12-ounce cans, many of them don't actually contain a full 12 ounces (net weight) of refrigerant. Usually, they'll run a bit short, and the DIYer ends up with a system that's somewhat undercharged, under-performing, and left wondering why it's not working right. For a "cool" running system, it pays to know exactly how much refrigerant you're putting in. Thus a high-quality refrigerant scale is an important part of an MVAC toolkit.

just for S&G, i checked the price of 30lb tanks. this has got to be a scam right?: