ACDelco GM Original Equipment 10-108 (12378255) Cooling System Sealing Tabs - 4 g (Pack of 5)

These work awesome! Do not bother with the other stop leak products!! I used a few of these to stop a leak in a 2005 Honda Element heater core months ago for a broke friend. Saved them a $800+ shop bill. Stopped the overheating issues due to coolant loss. Excellent product!!!

I have a 2013 Prius, 3rd generation . 210,000 miles. It had been running perfect, when it developed very rough engine noise and severe shaking from time to time when starting. Once underway the car ran normal. A couple of well reviewed mechanics were unable to figure out the cause of the problem. One even said the engine had something lose inside and wasn't worth fixing and should be sold for junk. That made no sense to me. Said he would give me $500 for the car as a trade on one of the used cars he had for sale. The other mechanic said he was certain the head gasket was not leaking (I suspected it was the problem until I got that advice)The check engine light came on and the code said the problem was with the #2 cylinder.I decided to use the internet to find an answer. Turns out this generation of Prius often suffers from the head gasket leaking a bit of water often into the number 2 cylinder. It's a somewhat common problem at around 200,000 miles.Number of options. 1, replace engine with a new or rebuilt or use a low mileage engine from Japan. 2. replace the head gasket. Costly options on an older car with lots of miles.fortunately, I came across a retired mechanic who was aware of the problem and suggested as a first and least costly option, I buy and use this AC Delco product to try and stop the leak. Said he used it on his own car with good luck. Said he was into the second year after using it once and no leaks.I bought it and put into the engine per the instructions. It has now been over 1000 miles since I used the product, only one application, and NO PROBLEMS!!! Talk about a cheap and effective fix. Plus it pin points the cause of the problem. So much for considering top mechanics as the last and best word on my problem.Two lessons learned. 1. This a great product so far. If problem shows up again I will just repeat the fix and take from there. Could not ask for more. 2. The internet is wonderful tool to use to help solve a problem, if only you will take the time and effort to use it fully.

I had a slight leak in the water pump of my Saab . Removal of the pump is quite a tough job on this car . I crushed up two of these tablets and added it into the coolant reservoir . After one day of driving the leak was gone . It's been almost 6 months now and still no leak .

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.

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.

A wonderful product for insuring that a major cooling system repair doesn't have any seepages or dribble leaks after a lengthy labor operation.

Working as described so far. Thanks!

It seals almost immediately. The first time I used a whole pack and my coolant was brown about few months later. I tried 2 tablets to see if my coolant will retain its color in a few months.