Epoxy is no longer the prefered option. Acrylic is the recommended product for sealing leakage from porosity and cracks. It is low viscosity and self penetrating. You can apply it yourself as it needs no special tools just a high pressure compresed air gun to blast the defect clear of debris. Drip feed directly onto defect. Impregnant cures in 3 to 5 minutes. Excellent temp, pressure and chemical resistance especialy to antifreeze and oil. Acrylic imprenants are also approved by US MIL-17563C Specification. Supplier "email@example.com" Product name: Acrylic120. Can be purchased on line. Also see web: "www.x-seal.co.uk"