

🚀 Seal leaks fast, drive worry-free—because downtime is not an option!
K-Seal ST5516 Heavy-Duty is a professional-grade, one-step coolant leak repair solution that permanently seals cracks and holes in water-cooled engines. Compatible with all antifreeze types, it requires no system draining or flushing and is engineered for heavy-duty commercial and agricultural vehicles. Trusted by mechanics worldwide and independently tested to ASTM standards, it delivers fast, reliable, and clog-free performance to extend engine life and prevent costly repairs.



| ASIN | B002BJEG3U |
| Best Sellers Rank | #36,905 in Automotive ( See Top 100 in Automotive ) #98 in Antifreezes & Coolants |
| Brand | K-Seal |
| Customer Reviews | 4.4 4.4 out of 5 stars (1,483) |
| Date First Available | 7 August 2012 |
| Item Weight | 540 g |
| Item model number | ST5516HD |
| Manufacturer | Solv-Tec |
| Manufacturer Part Number | ST5516 |
| Model | ST5516HD |
| Product Dimensions | 14.99 x 10.41 x 4.83 cm; 540 g |
A**N
Very effective with intake gasket coolant leak
I had an unsatisfactory result with one of my cars I earlier reviewed. However, I had a visible gakset leak between the plastic intake manifold and cylinder head in 2007 Town Car, and was about to remove it for servicing until I thought, let me give K-Seal another shot since I had a small quantity left. The result was magic! The leak is gone, and been running dry and clean for a month now.
T**Y
Good product. Quick delivery.
Happy with the product.
D**G
I have 2015 long nose Peterbilt. Had a slow cold leak from the bottom of the radiator (only would leak as the engine cools down) then I would have to add about 1 litre of coolant the next morning. After I added this product a few weeks ago, I’ve added nothing and the coolant level is still at the top. Excellent quick fix rather than new radiator.
J**S
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.
A**R
There was a crack in head gasket of my car and coolant was leaking from there. Results in engine overheating. I added Kseal HD in in coolant and I had driven 5000 KM after that and crack is healed hence no overheating. Authorised service centre had asked to change the head gasket , that could have costed me around Rs. 75000. Local mechanic suggested to weld the crack. That too have costed around Rs. 20000. But Kseal costed me only Rs. 3500. And it really worked for me.
A**O
Funciona y es fácil de usar
R**S
Had coolant leaking from water pump seal on a 2017 Ford Explorer. Used per directions and the leak stopped. A lot cheaper than replacing a water pump.
Trustpilot
3 days ago
2 weeks ago