K&W 401224 FiberLock Head Gasket & Block Repair - 32 Fl Oz

used this to fix a hairline crack somewhere in the block or timing cover. so i have a 2010 jeep grand cherokee with a 5.7 hemi motor, bought it real cheap due to haveing a head gasket issue due to an overheat , im a tech for 40 years and know these hemi's well ,i did all the work myself , replaced both head gasket heads were sent out and resurfaced and i did a valve job , the motor fired right up and ran perfect when finished , however i noticed my coolant level was dropping slowley with know external leaks , after investigating i found coolant in my catch can so know i knew that it was getting into the crankcase, after i drained out about 8 0z of oil from the sump i saw a little bit of coolant in there but not to bad and not a lot . the coolant seemed to be entering the crankcase but more as a vapor if anything because most was in my catch can. there was a hairline crack somewhere . i decided to try this but was very skeptical . and low and behold it worked ! i couldn't believe it , no more coolant in my catch can or in the bottom of oil sump , i was amazed it actually worked , its been a year now with about 7k miles and still holding up! no coolant loss ,no heater core or radiator issues, i did put a new thermostat in it after about 100 miles running on it and found some hardened material around it but i wasn't worried about it after i installed a new one . i recommend this if you have a small leak due to a crack .

I have a suspicion that the bad reviews of this product are coming from people who are using it incorrectly. I had a blown head gasket (confirmed by repair shop when they replaced my timing belt, water pump, and thermostat) on a 1995 1.5L Honda Civic engine. The only reason I picked up a bottle of this sealant was because the mechanic recommended it after I told him that I couldn't afford a $500 dollar repair bill for replacing the head gasket. The mechanic told me that he'd used this stuff before and that it was pretty much the only head gasket sealant on the market that he'd ever seen work and told me that he would never recommend any other but this stuff actually works. So I ordered a bottle and gave it a try. The first thing I noticed was that the instructions clearly state that you should read the entire label before starting and that you should know exactly how much fluid your radiator and engine block hold and to use a specific amount based on the volume. It also clearly states that if your water pump or thermostat are not properly working that it will not work properly and could cause uneven distribution of the product. It states clearly on the label to use the proper amount and to add it very slowly into the properly diluted radiator fluid and not to add the product until the fluid level is high enough not to touch the fins on the inside of the radiator. After doing just that, letting the engine run and the coolant cycle and then topping it off, and then letting it idle for over 15 minutes with the heat on, I could already tell that the engine was running as smoothly as it did before the blown gasket. After several days of driving, it no longer overheats, no longer produces white smoke from the coolant leaking through the gasket into the engine, no long is leaking oil into the coolant and is no longer running rough. The stuff is very clumpy and can look worrying but when the proper amount (for me 1/3 a bottle) is added to properly mixed 50/50 fluid, it cycles through and smooths out. I plan on letting it stay in the engine until I get ready to flush the radiator out and get the rest off the product out but the bottle clearly states that you can leave it in without flushing and that it will not cause clogging or sludge. So far it has work perfectly and seems to have sealed the gasket completely but even if it does begin to leak slightly, it says that you can add more which I plan to do if it does, though so far it after 4 days of daily commuting for 36 miles, it has had no problems and works perfectly. I'd recommend it to anyone who can properly follow instructions but I would imagine that if you added it to the wrong coolant type or mixture or if you added way more than was intended that it would cause major problems with clogging up your system. Having a new water pump probably also helps, as I would imagine that if your water pump wasn't properly cycling the stuff that it would clog up in the system and prevent the sealant from reaching the leaking points and possibly clog up the radiator or heater coils. Use it as intended and it should turn out just fine.

I strongly advise persons to use this product with extreme caution. I am confident that I fully understood the directions before use but still ended up with a plugged thermostat and plugged heater core in my F-150 pickup with 3.5l Ecoboost. After spending $700 to get the thermostat replaced, heater core unplugged, and closed cooling system flushed and refilled I ended up right back where I started from with a slow coolant loss.

Van motor was blowing white smoke and using a lot of water. Instructions said to use half of bottle of product for size of water system. It only would take quarter of bottle as that’s all that would go in. System was full. So follow the rest of instructions. Two weeks now no leaks. Amazing stuff. I have use the cleaper version of this stuff years ago and also had amazingly results.

sealed a damaged head gasket and or cracked head the was leaking very slightly where it would get tiny air bubbles in the radiator. temperature was running at 50% means (needle half way on gauge) with out thermostat and electric fan on full time so basically still drivable. it was a 3 cylinder diesel engine. after adding this according to instructions it stopped the bubbles and temperature down to 25%. it did clog the radiator a few hours and drive cycles later but it was flushable. I only used 1/3 bottle maybe even a little less. running it 1 month still good. however i tried it on a Toyota 22r engine with a severe head gasket case where water would enter the oil and compression into cooling system. it didn't work. it tried to for a few seconds or a minute things sounded better but didn't work even after second application. I even tried removing the spark plug on 1 of the bad cylinders to see it that would help give it time to seal with out the extra compression blowing out but it failed to work. basically it works on minor leaks but not major ones. save your money on the major leaks which is as expected.