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

Have a Silverado with the 5.3l. Had a leak that I couldn’t find without tearing everything apart. More than likely the manifolds on the side of the radiator, as this is common on these trucks. Didn’t want to change a radiator this month before a short trip to the mountains.Broke the tablets up. Dropped in reservoir. Drove for 30 minutes. Let it cool down and set in. No more leak.Easiest and cheapest fix I have ever witnessed. Not sure how long it will last but so far it has lasted a month and driving off road on some rough stuff. I blew out a CV axle but not my coolant leak!

I’m extremely surprised. I was having a pretty decent leak coming from my timing cover and I put two tablets in. Within about 25 minutes the leak slowed a lot and eventually stopped. I originally could only drive about 20 miles until I lost all coolant and started to overheat. The only downside is that your coolant will turn a murky color and if when you do repair your car you would most likely need to get the coolant changed out.

Seems to be holding liquid in radiator. Would purchase again

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.

Tried it for just a few times but cleans good. Like most window cleaners they leave a residue on the glass outside the wiper area lol

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.

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.

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