--- product_id: 8435813 title: "K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required" brand: "k-seal" price: "Β£23.49" currency: GBP in_stock: true reviews_count: 13 category: "K Seal" url: https://www.desertcart.co.uk/products/8435813-k-seal-st5516-heavy-duty-multi-purpose-one-step-coolant store_origin: GB region: United Kingdom --- # One-step, no flushing needed Heavy-duty for large engines Seals leaks in minutes K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required **Brand:** k-seal **Price:** Β£23.49 **Availability:** βœ… In Stock ## Summary > πŸš€ Seal leaks like a proβ€”fast, permanent, and hassle-free! ## Quick Answers - **What is this?** K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required by k-seal - **How much does it cost?** Β£23.49 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.co.uk](https://www.desertcart.co.uk/products/8435813-k-seal-st5516-heavy-duty-multi-purpose-one-step-coolant) ## Best For - k-seal enthusiasts ## Why This Product - Trusted k-seal brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - β€’ **Instant Leak Fix:** Stop coolant leaks fast with a formula that seals holes & cracks in minutes. - β€’ **Effortless Application:** Shake, pour, and goβ€”no draining or flushing required for busy pros. - β€’ **Universal Compatibility:** Works seamlessly with all antifreeze types across commercial & agricultural vehicles. - β€’ **Engineered for Heavy-Duty:** Designed for large engines, from trucks to tractors, ensuring permanent repairs. - β€’ **Trusted Professional Grade:** Mechanic-approved, non-corrosive, and independently tested for lasting reliability. ## Overview K-Seal ST5516 Heavy-Duty is a professional-grade, one-step coolant leak repair solution that permanently seals leaks in radiators, head gaskets, freeze plugs, and more. Compatible with all antifreeze types, it requires no draining or flushing and is engineered for heavy-duty commercial and agricultural engines. Trusted by mechanics worldwide, it delivers fast, durable repairs that extend engine life and prevent costly downtime. ## Description Product description Find the Right K-Seal Product K-Seal Coolant Leak Repair K-Seal Head Gasket Repair K-Seal HD Coolant Leak Repair Best Application For everyday coolant leaks in cars, motorcycles, and light trucks. For head gasket leaks, cracked heads, and porous block problems. For larger engines, HGVs, tractors, heavy plant, and commercial vehicles. Shake, Pour & Go Easy one-step formula. Just shake, pour, and go. No draining or flushing needed. Simple pour-and-go formula for head gasket and block repair. Heavy-duty pour-and-go formula designed for larger cooling systems. Seals Common Leaks Helps seal leaks in radiators, heater cores, water pumps, freeze plugs & blocks. Helps repair blown head gaskets, cracked heads, and porous blocks. Helps seal leaks in radiators, head gaskets, heater cores, water pumps & blocks. Coolant Compatible Works with all types of antifreeze and coolant. Works with all water-cooled engines and common coolant types. Compatible with antifreeze and coolant systems in larger engines. System Capacity 8 fl. oz. bottle treats cooling systems up to 20 quarts. 16 fl. oz. bottle for head gasket and block repair applications. 16 fl. oz. bottle treats larger cooling systems up to 60 quarts. Review: Worked Perfectly! - Vehicle leaking coolant, about 1gal per 1,000 mi driven. Dealer diagnosed as jiffy tight fittings on turbos with a repair estimate of $3,300. 2015 Ford F-150 - 3.5L Ecoboost with 140K miles so didn't want to put that kind of cash into a high mileage vehicle. Added as directed and leaks stopped immediately. 1K miles later, coolant level in the overflow tank has not gone down at all. Review: This stuff save me about $20K! It works! - I waited 5 days to write this review on my birthday. Mainly because I am so impressed with this product and I didn't know that it would hold. I'm not getting paid for this review and I rarely write reviews. A little history. I own a 2007 Mercedes E-63. This car is a beast and is a joy to drive. The dealership diagnosed a blown head gasket on the car. The report shows coolant mixed with the engine oil. My oil almost looked like a mocha espresso. A very bad sign. The car was immediately overheating. I was adding antifreeze every day. The dealership estimated repairs to start at $15K but could easily rise to $25K. Once the top of the motor is opened up I'm sure they would recommend new cams (4), new cam adjusters and of course new seals. A new crate engine for this car from Mercedes-Benz costs $57,000.00. After carefully reading the directions I added coolant with the bottle of K-seal after shaking it for 1 minute. Then I drove the car normally for 20-25 minutes. The car came up to temperature and stayed there. It didn't overheat! After feeling terribly about having to sell the car as a mechanic's special or donating the car I can instead enjoy driving the car daily. I did end up changing the oil 3 times before it didn't appear to have any more coolant in it. Thanks K-seal! ## Features - FIX IT FAST: Our multi-purpose solution works in minutes to quickly seal leaks in the radiator, head gasket, freeze plugs, block, heater matrix & water pump of heavy duty vehicles. Fixes most leaks in water-cooled engines - STOP HOLES & CRACKS: With 1 step our unique formula will seek out each hole & crack, sealing them, without any adverse impact on the efficiency of your engine cooling - HEAVY DUTY PERFORMANCE: Engineered for large engines & industrial use; suitable for commercial or agricultural vehicles. Compatible with all types of antifreeze coolant ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B002BJEG3U | | Best Sellers Rank | #11,469 in Automotive ( See Top 100 in Automotive ) #49 in Antifreezes & Coolants | | Brand | K-Seal | | Customer Reviews | 4.4 4.4 out of 5 stars (1,623) | | Date First Available | May 29, 2009 | | Is Discontinued By Manufacturer | No | | Item Weight | 1.19 pounds | | Item model number | ST5516HD | | Manufacturer | Solv-Tec | | Manufacturer Part Number | ST5516 | | Model | ST5516HD | | Product Dimensions | 5.9 x 4.1 x 1.9 inches | ## Images ![K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required - Image 1](https://m.media-amazon.com/images/I/71MW1pVoIUL.jpg) ![K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required - Image 2](https://m.media-amazon.com/images/I/711qxdv5xHL.jpg) ![K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required - Image 3](https://m.media-amazon.com/images/I/81Js2ztN+RL.jpg) ![K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required - Image 4](https://m.media-amazon.com/images/I/81367JDTP5L.jpg) ![K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required - Image 5](https://m.media-amazon.com/images/I/81sAcKFs57L.jpg) ## Questions & Answers **Q: Does it work on potentially warped heads** A: No idea **Q: how much do i need to pour in a diesel 1 ton cummins** A: You need this one bottle for a Dodge 3500 hd. I have this one bottle in my HD Freightliner 330hp MBZ engine hauling freight (54,000 lbs cap) 6 days a week and it stopped my coolant leak in the engine bay and heater core with no blockage and no. My opinion, Many reviews say products dont work BECAUSE most people dont take care of their equipment and their vehicles are old, high mileage and no maintenance done. None of the add to a tank products are as good as replacing with new parts but thats expensive, we get it. This may or may not fix your problem but its a low cost gamble with a high probability of success. Dont listen to the negative reviews. If the problem comes back, your damage was too far gone and in need of replacement anyway. **Q: Will this work with aluminum heads?** A: It works equally well with cast iron or aluminum. Great Stuff. Not a long-term solution, but it will buy you a lot of time. **Q: Tried using alumaseal, which isn't working. will i need to flush the system before using the k-seal?** A: I used the HD Truck bottle on my 1998 GEO Tracker ( used 1/3 of the bottle ) of K-Seal and it worked. I have used so many to no avail. To answer your question, I must have @ least 3 to 4 other sealers in my colling system when I added K-Seal. It's been almost a year & no adverse effects having not flushed my radiator. Should I have flushed the radiator & the system? Yes, I should have. ## Customer Reviews ### ⭐⭐⭐⭐⭐ Worked Perfectly! *by J***S on December 17, 2025* Vehicle leaking coolant, about 1gal per 1,000 mi driven. Dealer diagnosed as jiffy tight fittings on turbos with a repair estimate of $3,300. 2015 Ford F-150 - 3.5L Ecoboost with 140K miles so didn't want to put that kind of cash into a high mileage vehicle. Added as directed and leaks stopped immediately. 1K miles later, coolant level in the overflow tank has not gone down at all. ### ⭐⭐⭐⭐⭐ This stuff save me about $20K! It works! *by M***S on August 14, 2025* I waited 5 days to write this review on my birthday. Mainly because I am so impressed with this product and I didn't know that it would hold. I'm not getting paid for this review and I rarely write reviews. A little history. I own a 2007 Mercedes E-63. This car is a beast and is a joy to drive. The dealership diagnosed a blown head gasket on the car. The report shows coolant mixed with the engine oil. My oil almost looked like a mocha espresso. A very bad sign. The car was immediately overheating. I was adding antifreeze every day. The dealership estimated repairs to start at $15K but could easily rise to $25K. Once the top of the motor is opened up I'm sure they would recommend new cams (4), new cam adjusters and of course new seals. A new crate engine for this car from Mercedes-Benz costs $57,000.00. After carefully reading the directions I added coolant with the bottle of K-seal after shaking it for 1 minute. Then I drove the car normally for 20-25 minutes. The car came up to temperature and stayed there. It didn't overheat! After feeling terribly about having to sell the car as a mechanic's special or donating the car I can instead enjoy driving the car daily. I did end up changing the oil 3 times before it didn't appear to have any more coolant in it. Thanks K-seal! ### ⭐⭐⭐⭐⭐ It'll work on anything but bullet holes I think. *by I***N on November 21, 2025* I just concluded a 7,000 mile drive from Georgia to Oklahoma, then to Cali and from there, Washington state and then back to Georgia in my 2002 Chevy Tahoe while hauling a 21' toy hauler heavy laden with toys. My Tahoe has an aftermarket radiator that produced a pinhole leak during travel. I couldn't directly locate the leak nor was I able to just replace the radiator as I was traveling. So I considered using a radiator stop leak but hesitant to do so as I didn't want to plug up my cooling system at all. I found this product and due to the reviews, decided to try it. It worked almost immediately after running the engine for a while to circulate the solution. And it still has not shown signs of leaking and no affect of the cooling capabilities either. I highly recommend this product! ## Frequently Bought Together - K-Seal ST5516 Heavy-Duty Multi-Purpose One Step Permanent Coolant Leak Repair, 16 oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required - PEAK 50/50 Prediluted Antifreeze and Coolant for All Engine Cooling Systems - K-Seal ST3501 Pour and Go Head Gasket Sealer, 16oz, Permanent Repair for Blown Head Gaskets, Cracked Heads and Blocks --- ## Why Shop on Desertcart? - πŸ›’ **Trusted by 1.3+ Million Shoppers** β€” Serving international shoppers since 2016 - 🌍 **Shop Globally** β€” Access 737+ million products across 21 categories - πŸ’° **No Hidden Fees** β€” All customs, duties, and taxes included in the price - πŸ”„ **15-Day Free Returns** β€” Hassle-free returns (30 days for PRO members) - πŸ”’ **Secure Payments** β€” Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** β€” Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.co.uk/products/8435813-k-seal-st5516-heavy-duty-multi-purpose-one-step-coolant](https://www.desertcart.co.uk/products/8435813-k-seal-st5516-heavy-duty-multi-purpose-one-step-coolant) --- *Product available on Desertcart United Kingdom* *Store origin: GB* *Last updated: 2026-05-26*