A/C sealant OK to use? - PeachParts Mercedes-Benz Forum

Capn Jonas · #1 07-24-2018, 01:02 PM

My 1990 300D A/C system leaks down after a couple of weeks. I've had a can of A/C Stop Leak in my shop for a few years. Are these additives safe to use and are they effective?

Thanks

bsmuwk · #2 07-24-2018, 01:08 PM

it swells seals. it's like putting rubber in a parts washer. it'll probably work initially, but in the long term you just destroyed every seal in that system.

would i use it? nope. it's easy enough to find leaks in AC systems with dye. not sure what your capability is, but next time you pump it full, use freon with dye. over the course of your few weeks, run over the system with UV (or take it to an AC shop just to find the leak with their lights). I'd almost bet it's the compressor shaft seal or the orings atop the compressor.

vstech · #3 07-24-2018, 01:44 PM

Quote:

Originally Posted by bsmuwk

it swells seals. it's like putting rubber in a parts washer. it'll probably work initially, but in the long term you just destroyed every seal in that system.

would i use it? nope. it's easy enough to find leaks in AC systems with dye. not sure what your capability is, but next time you pump it full, use freon with dye. over the course of your few weeks, run over the system with UV (or take it to an AC shop just to find the leak with their lights). I'd almost bet it's the compressor shaft seal or the orings atop the compressor.

No... you are thinking of transmission or power steering stop leak...

Ac stop leak come in a variety of formulas but they all work by blocking leaks... either by reacting with moisture, or building up a barrier... some are ok, some will solidify in your system and ruin everything...

Be warned which type you have.

Capn Jonas · #4 07-24-2018, 07:39 PM

I'd appreciate your experience re one or two that work well.

shertex · #5 07-24-2018, 10:29 PM

Cryoseal works very well but is pretty pricey.

SSR R-134a Kit Repairs Leaks In Mobile Air Conditioning Systems

I had good success with it sealing an evaporator leak.

I've heard good reports on the products from ES Refrigerants and would not hesitate to try their products.

https://www.es-refrigerants.com/

It would help to know the source of your leak.

BillGrissom · #6 07-26-2018, 08:03 PM

Duracool sells one. Never used, I just saw when buying their refrigerant and oils. I agree that finding the leak and changing O-rings or hose is best. Many oils come w/ uV dye and I have found the leak just from the yellow dye in ambient light.

lorainfurniture · #7 07-26-2018, 08:34 PM

Quote:

Originally Posted by Capn Jonas

My 1990 300D A/C system leaks down after a couple of weeks. I've had a can of A/C Stop Leak in my shop for a few years. Are these additives safe to use and are they effective?

Thanks

If you are leaking 2 pounds of refrigerant in 2 weeks no leak sealer in the world will help you. That’s a huge leak.

Bigdaddybenz · #8 07-28-2018, 11:19 AM

DON'T DO IT!!!!!..... IT WILL CLOG YOUR EXPANSION VALVE...... and if you've ever had to change the expansion valve, as I have had to do, on a W126, you'll never want to do it again!!

Far better to simply replace all of the o-rings at the various connectors, it's not so difficult...... there's no quick fix to anything..... do it right the first time and keep movin on!!

Graham · #9 07-28-2018, 08:56 PM

I had a leak in our E320 A/C. I bought a leak stopper at Walmart in SC - Interdynamics. It stopped the leak and I had colder A/C than ever. This about a week before heading home to Canada. Day we left was hot. The A/C blew about 10 miles into our trip. Zero pressure after that! Seems the plastic evaporator blew. I knew that was where the leak was (from dye).

I have never fixed it. Dismantling dash on E320 is no easy task. 20 hrs at dealer, IIRC.

shertex · #10 07-31-2018, 11:10 AM

Quote:

Originally Posted by Bigdaddybenz

DON'T DO IT!!!!!..... IT WILL CLOG YOUR EXPANSION VALVE...... and if you've ever had to change the expansion valve, as I have had to do, on a W126, you'll never want to do it again!!

Far better to simply replace all of the o-rings at the various connectors, it's not so difficult...... there's no quick fix to anything..... do it right the first time and keep movin on!!

Not all sealants are created equal. There's no chance that Cryoseal will clog anything. But, the leak has to be slow enough, and in the right place (for example, Cryoseal won't address compressor shaft seal leaks).

A common weak spot for these cars is the evaporator. For many of us, who have neither the skill set nor the patience to replace an evaporator....and who are unwilling to pay our mechanic $2000 to do it...a quality sealant is the obvious choice.