I have a Chevy S10 it would take two to three weeks for the freon to leak out. So it was a small leak I've been a mechanic for 50 years this is possibly the worst stop like I have ever used. I strongly suggest you look for something else

...have not noticed any issues as of yet. Need to complete a vacuum test to verify effectiveness.

It really works one month and going strong. Evaporator leak fixed. Same leak happened three years ago after original leak occurred when it was also three years old. Seems that manufacturer had defective evaporation coils since we had original evaporator coil leak from corrosion. installed again in hopes that they updated their part. Guess they didn’t of allowed defective part to be sold.

So I am a home mechanic. And that means I save money. When you save money you can afford to spend a little to save a lot and that is what I did. 2009 Toyota Avalon started to leak at 200,000 miles. I would put in a partial can about once every 6 month and then a month and then a week. Each time doing what I did car after car before.Finally I bought a vacuum pump and gauges. I got a deal locally and see even a better deal on Amazon for a combo at about $119.00, get it and be happy. I am not a pro and I do or did not need a mega expensive system.I bought this stop leak and some dye along with a detector light and glasses (glasses useless) turned out after this goo stop stuff those glasses and dye were not needed since there was no leak after.Anyway stick with me here because the following is important.I put the A/C Zero leak into the yellow tube from the gauge manifold. It does not mater from which side just keep both sides up to keep it in and then connect the can and hose back up in a mater that keeps it in the tube. Yes it is messy. What is IMPORTANT is this. "Once the can is opened and freon has gone into your system and enough freon is in to start the A/C pump and another can or partial is put in to get the Gauges at Low side 30PSI and high side at 145PSI or a little less for my car. Keep the car running.Did you catch the last part KEEP THE CAR RUNNING. That pump in your A/C system likely flows very very slow and it has many feet of tubing...what maybe 100 feet when you figure the side to side to side in the evaporator and condenser and then the dryer and the delivery and return tubes. My point is leave it running for an hour or two so the leak stuff can get in the entire system and find the leak. Even if it is cold outside , leave the A/C on with the heat. A/C draws moisture out of your car and the pump can circulate that even when the heat is on. That is how the defrost works you know. DRY AIR blowing heat using the A/C and the heater core at the same time. Anyway. My A/C is ice cold and hanging in there. I expect to put the other half of the A/C Zero-Leak in if needed and will update if I do. I planned to pay $2000 for a new A/C if this did not work because it is cheaper than a new car , also the Avalon is a sweet fast riding car and it is paid for. Good luck for your first try"

This product worked for me, it fixed what appeared to be a large leak on the A/C evaporator core on my 2008 Trailblazer. It was my last ditch effort before having to chose between paying over $1,000 in labor + parts, or to spend 2+ days and approx. $300 in parts replacing the evap core myself. No A/C while sitting in traffic at temperatures consistently above 88F year-round (rarely dipping below 70F even during "winter") here in South Florida is not really an option. Like in most vehicles, to replace the evap core on a Trailblazer you have to remove the entire dashboard, center console, steering wheel, radio, sound amplifier, and all sorts of wiring and connectors just to be able to get to and remove the plastic enclosure that houses the evaporator core, definitively not a short weekend project unless you are a professional who does this for a living.Long story short, none of the other highly rated stop-leak products I tried before Comstar A/C Zero Leak worked. I recharged the A/C system three times (4-8Oz or more of the stop-leak product plus pure R134-a refrigerant) each time using a different product and following the manufacturer's directions. I was careful to use only products that claimed not to ruin your compressor, accumulator, orifice tube, or to clog your A/C system, every time, the A/C would go from freezing cold right after recharging it back to blowing hot air within 2-3 days max. This SUV is a retired undercover unit I bought at a Police surplus auction, I'm pretty sure their maintenance crew tried to fix the issue before decommissioning the vehicle, everything else on it works just fine.Two months ago I purchased this product (Comstar A/C Zero Leak, 4 oz.) and an A/C repair kit that includes a vacuum pump, manifold gauges, vacuum pump oil, hoses, and accessories ( https://www.amazon.com/gp/product/B077PY6NHR/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1 ), I also purchased 4 Oz PAG oil and enough pure R134-a refrigerant to refill the system, all for less than $170. I took the SUV to my mechanic to have the A/C evacuated using the proper equipment ( most A/C shops do this for free around here), then I added a approximately 2 ounces of this product by pouring it directly into the hose connected to the low pressure port before opening any valves, and proceeded to recharge the system with some PAG oil (2 Oz in my case) and the amount of R134-a as specified in the owner's manual. SUCCESS!It's been two months since I did this, and my A/C remains so cold that I rarely have to bring the controls above the minimum fan speed on this sweltering Florida summer. I use a bluetooth OBD II reader with a mobile app to keep an eye on my A/C internal pressure (reported by the high pressure sensor) along with the engine and transmission temperatures, my A/C high pressure hasn't dropped at all during this time. I don't know if this will keep my A/C working months or years, but so far so good.