

🛡️ Seal it once, drive forever — the ultimate fix for fearless road warriors!
K&W 401016 Block Seal Permanent Metallic™ is a professional-grade, 16 oz sealant that forms a permanent molecular bond as strong as steel. It effectively seals cracks and holes in cast iron and aluminum engine blocks, head gaskets, freeze plugs, and radiators for all water-cooled diesel and gasoline vehicles. Engineered to withstand extreme pressure and temperature, it surpasses ASTM D6107 standards and is independently tested and rated #1 for cooling system leak repairs.

| Customer Reviews | 4.1 out of 5 stars 378 Reviews |
G**E
Works great
Very good product
B**N
Quality
Works as it should
A**A
Haven't used it yet, but know it works
😄
T**T
then fill it with tap water and then poor this bottle into the radiator cap opening
These do work! With certain assumption, depends on the leak or crack in your head gasket. I followed the directions from TrustMyMechanic . com in the you tube channel. [...] . His directions made more sense to me. You really have to drain your existing coolant out, flush it a couple of times, then fill it with tap water and then poor this bottle into the radiator cap opening. Then just drive your car for at least 500 miles. It took me about a week of driving to work and back to hit 500 miles. I check my radiator every day to top it off with water before going to work and noticed it stop leaking after about 75 miles on the odometer. So what does that mean...you really have to drive it around, get the engine hot enough and let the water/block seal get into the seams of the crack/leak. The directions on the bottle may work, but I think by doing it this way, I think it works a lot better. Like I said, it stopped leaking at around 75 miles into the 500 miles. I guess if you drive it over 500 miles and it is still leaking, then I think the crack/leak is way to big for this product to work. Or it could be leaking outside of the cylinder head. So after the 500 miles, verify that it stopped leaking by openning up your radiator cap and looking into your radiator. The top of the radiator should still be wet, there should still be water floating around at the top. If you can see the radiator fins and it's bone dry, then you still have a leak. If you are good, drain the tap water/block sealer, then flush it a couple of times. Then fill it up with coolant for your car. I use this product on a 2005 Toyota Tacoma Pre-Runner. Symptom of a crack/leak in your head gasket: Got a P0300 (random misfire), P0304 (cylinder 4 misfire), P0306 (cylinder 6 misfire). For this truck, when you drive it around town, you can hear water swooshing back and forth inside the engine bay. This is because when there is a leak in the gasket, the pressure and gases from the cylinder head pushes back into the coolant chambers and creates bubbles/air pockets thus there is open space in your coolant block that allows the coolant to move around. So if you hear that, it's an indication that you got coolant issues. Also, you will be losing coolant everyday or two when you check your radiator. Hope that helps...
R**P
Past shelf life when delivered
After lots or research, I settled on this product, prepared me vehicle and waited for a week for it to show up. When it arrived I followed the instructions to a tee, when I opened the can and poured it into the gallon just, after vigorously shaking it as per the instructions, the business part of the product had solidified in the bottom of the can rendering completely useless. DO NOT WASTE YOUR MONEY
A**R
The bottom quarter of the can was solid.
I really needed this product. Please make sure the bottom part is not crystallized.
A**R
The Best One
It was my third and final attemp to fix my head gasket. My friend told me about this product and how well it work. We followed the direction to a tee. Sealed up perfect no leaks to this day. Thank You 😊
D**.
Fixed oil in water problem
Seems to work. I let car run for 3 hours and water in oil evaperated. Do what the can says.
Trustpilot
2 days ago
4 days ago