Bar's Leaks 1109 Liquid Copper Block Seal, Intake and Radiator Stop Leak, 18 oz. | One Step, Safe for All Cooling Systems

I've used this stuff twice in 20 years and both time it worked great. The first was in a 1998 grand cherokee that was driven across town with low coolant resulting in a blown head gasket or cracked cylinder head. The second a 2002 S10 v6 that ran great but consumed a half gallon of coolant every few days. In both cases I added the full bottle and drove the car. In the case of the S10 it took a couple days driving to work but it's been a month now and no leaks. Saved me a ton of work replacing the head gasket and/or cylinder head(s).

OMG thank you for this wonderful product!! I used it in my old skid steer which was leaking a lot and overheating. Replacing the radiator does not seem to be an option- it’s above my ability and can’t find a mechanic to work on it. I had tried other radiator seal products with unsustainable results. As a last ditch effort I ordered this Bar’s copper block seal and it WORKS!!!! It has been several months and is still working, I am so very happy. The cost is a bit higher than the other products that did not work. For any future problems I won’t waste my money on cheaper products, this product is totally worth the extra few dollars. In the end it has literally saved me hundreds of dollars.

Gonna give it 4 stars because my husband used it before and its worked. But for my van it didnt and it was a issue that this couldn't solve. So could return it. That the only downfall but my husband recommended it and has used it before.

I had a minor coolant leak coming out the passenger rear side of my block, about several drops after engine shutdown, small head gasket leak. I added a bottle of this stuff and it seemed to have stop the leak...been several months so far. So far, so good. 1997 Ford F150 4.6 V8 with 140k miles. Engine has never been apart.

works good

Used as directed. Didn't work on first drive. Going to give it few days and see what happens.

Bar’s Leaks Liquid Copper Block Seal really delivers. The one‑step formula makes it simple to use—just pour it in and let it circulate. Within a short time, it sealed a small radiator leak and stopped coolant loss without any complicated process or extra tools. The 18 oz. size is generous enough for most vehicles, and the copper formula feels more heavy‑duty compared to standard stop leaks. It saved me from an expensive repair and kept the engine running smoothly. For anyone dealing with minor intake or radiator leaks, this product is a reliable, cost‑effective solution that works exactly as advertised.

Summary: Product Failure and Systemic Coagulation As a technician with years of experience in thermal systems and specialized equipment maintenance, I have a high standard for manufacturer specifications. Unfortunately, Bar’s Leaks Liquid Copper failed to meet even the most basic safety margins for automotive cooling systems. Following a standard application to a maintained 2004 Pontiac Montana (3.4L V6), the product did not remain in suspension as advertised. Instead, it triggered a systemic chemical coagulation, turning the entire cooling system into a thick, copper-colored gel. This resulted in: Total Obstruction: The narrow passages of the throttle body heater became completely blocked, requiring an emergency bypass to keep the vehicle operational. Component Failure: The thermostat housing and spring mechanism were fouled with solidified residue, causing an immediate overheat condition. Emergency Remediation: A full system flush and parts replacement were required to prevent catastrophic head gasket failure. Technical Critique of Support Logic Upon contacting Bar’s Leaks Technical Support, the response was a textbook example of "corporate friction" designed to deflect liability. The support team attempted to attribute a total system gel-up to a minor dosage discrepancy (using a full bottle in a 10-quart system instead of the recommended half-bottle). From an engineering standpoint, a professional-grade additive should fail "gracefully." If a product's fail-state for a slight over-dosage is the total solidification of the engine's coolant, that product is fundamentally unstable and poses a significant risk to the consumer. Claims Process Experience The manufacturer’s claims process is intentionally cumbersome: Impossible Requirements: They requested a 6-to-8 oz fluid sample after I informed them the system required an immediate emergency flush to save the engine. Deflective Logic: They asserted that the product "couldn't" affect a thermostat until it opened, ignoring the fact that once the thermostat cycles, the suspended solids immediately foul the mechanism. Manual over Reality: The company relies on rigid manual citations to avoid addressing the actual chemical failure of their product in a clean, maintained environment. Final Verdict Bar’s Leaks appears to prioritize a "blame the customer" script over technical accountability. While they offer a refund of the product price as a fallback, they have shown zero willingness to cover the collateral damage caused by their product's unpredictable behavior. Technician's Note: Use with extreme caution. The risk of systemic clogging and expensive component replacement far outweighs any potential benefit of sealing a minor leak. To be fair, the Pontiac Montana (3.4L V6) is known to be sensitive to coolant additives. However, I haven't seen this before with other additives.

No more minor leaks . Water pump no more noise.

Did what it said and stopped a block leak in a 2007 Mazda 3. I only needed to use half the container, so I still have some left for another leak down the line. Not much else to say.

Bars a is always a good product . Just used as stock this round.

I was told my head gasket was going,after using Bar's it took only 2 bottles over a 2 month period and since then no more head gasket issues ,like over heating,my van runs good now.

Had a small leak around the joint on radiator and this unfortunately didn't do the trick. Neither did anything else we tried. I guess it depends where the leak is. It did however make everything glittery.