ACDelco GM Original Equipment 10-108 (12378255) Cooling System Sealing Tabs - 4 g

These tabs worked perfect on my Gen3 2010 Prius with a number 2 cylinder headgasket leak. This is a common issue for Prius between 2010 and 2014 and will show a misfire code in number 2 cylinder, loss of coolant and a rough cold start. Each tablet is equivalent to 4oz and you need 1 to 1.5 oz per quart of coolant in your cooling system. My Prius takes 7.7 quarts. So I crushed two tablets inside a zip lock bag, cut a corner and poured it into the expansion tank/coolant reservoir (since there isn't a radiator cap for the prius) and topped it off with original Toyota long life red coolant. I then drove it around foe about 3O mins cleared the check engine light with my scan tool and and drove it foe about 40mins until it went through and cleared all the monitors. No check engine light!!! Also, the next morning on cold start, no rough idle and car ran smoothly. Saved me a lot of money. Not sure how long it will hold up. Car currently has 250,000 miles. I will report at 260,000 miles to see how it holds up. I wouldn't recommend using more than necessary as it can clog the heater core and you will lose heat and have inefficient cooling when needed. Definitely saved me a few grand of replacing the headgasket. I will replace it eventually. Since it was leaking into the spark plug cylinder, I would replace the plugs as well with original ones from thr dealer and an oil change.

Sealed small coolant leak that I could not find pickup truck sat for weeks and what u know no more leaks I figured it is ac delco so it probably is safe..it all natural substance..for the price it is work it...highly recomend

For years my 22-year old GM 3800 Series 2 engine has been slowly consuming coolant with no visible leaks. All the online forums suggest the LIM gasket needs to be replaced, which is a very expensive job. Others advise never to use any "stop leak" in the cooling system as it will plug the heater core. Here is my experience, and the preliminary results are very encouraging.Separately I purchased an inexpensive (about $40) cooling system pressure test kit here on Amazon to perform a "before" and "after" leakdown test. Both tests were conducted when the coolant was at garage temperature, and both were started with an initial pump of pressure to 13 psi. The pressure gauge was read after 10 minutes elapsed. In the "before" case the pressure dropped to 9 psi, but in the "after" case the pressure remained steady and only slightly dipped to 12.8 psi! The tests were conducted just 24 hours apart.So it would seem the introduction of sealing tablets into the cooling system made a measurable difference. The vehicle's heater was still working fine at the conclusion of the 25 minute drive used to circulate the newly added tablets. I used ONLY 3 of the 5 tablets in my 12 quart capacity system. The 3 tablets were crushed to a powder and mixed with about 6 ounces of coolant removed from the radiator. There were no "globs" in the mixture when added back into the radiator.I did flush and replace the coolant about a week prior to adding the tablets, which is recommended.

I hate mechanic in a bottle fixes, unfortunately right now I didn't feel like pulling my aluminum radiator out to find another pinhole leak, previous crack is held with JB Weld radiator compound and worked awesome, new leak appears to be in an area I can't get to in the fins. Crushed up 4 tabs and put them in, took the truck out for a 45min drive and core support was bone dry, as of a week later still perfectly good, no issues. This is in an 80's Chevy truck with a 365 horse 350.

These things have been around since the dawn of time. GM used to put these in new cars off the line during the LIM-gasket fiasco. They work as intended most of the time and can even be a permanent repair in certain cases. I had a slight external head gasket leak from a crossover coolant port. The leak was tiny, a seep at best and these took a good little while to actually seal up such a tiny leak but they did after a couple hundred miles. The product works most of the time (within reason) and is worth a shot before doing more expensive repairs.My only complaint is the shipping from Amazon, once again they fumbled the packaging and shipping. They sent me an open package with one of the tabs completely missing. The envelope wasn't breached so it had to have been packed that way. Another one of many Amazon shipping gripes.

This sealed the porous Castech heads in my 5.3L LS engine in my 2002 Chevy Suburban. I too have the porous Castech heads. Slow leaks coolant into the engine. If you are loosing coolant but can't see where, check the oil sump when changing the oil and if you have gel-like black goop, that's the coolant after the water has been driven off by the heat. As others have suggested, crush a couple of tablets into a fine powder, thoroughly mix into either coolant or distilled water and pour into coolant tank and drive the vehicle immediately to circulate the stop-leak. I used to add about a quart of coolant with every fill up of the tank. This stopped the coolant loss immediately. At this point I have not had to add any coolant since I added this to the coolant.

I used these after talking to my brother in law who was a full time mechanic and he advised GM put these in all their cars coming off the line. I replaced the water pump in a 2006 caravan… 2 of the 5 bolts snapped off in block. Used this as a last resort to help the leaking of coolant from the pump. It works.. I will always have this handy.

We were quoted $3,800 to change the head and head gasket on our forklift at work. For $7 I figured this was worth a shot. Put 3 crushed tabs in the radiator and within 15 minutes our leak had completely stopped. It was leaking about a quart every 30 minutes so it wasn't a tiny leak. If it only lasts a few months it'll be worth it to try again. But we only use the forklift for 10 - 20 minutes a day so the repair might last for years. Fingers crossed!