Persistent leaks or unreliable seals on engine components can be irritating and costly. Permatex Ultra Black is the trusted solution for creating durable, oil-resistant gaskets that withstand heat and fluids.
With this guide, you’ll learn how to apply it like a pro, ensuring your repairs are solid, leak-free, and built to last.
1. Product Insights
Formula and Composition
Permatex Ultra Black is a specially RTV silicone for high oil resistance. Its composition allows it to withstand prolonged exposure to automotive fluids like oil, coolant, and transmission fluid, making it a versatile option for engine repairs.
Unlike conventional gaskets, it forms a seal directly on the part’s surface, creating a custom fit that accommodates irregularities and imperfections.
Intended Use
This product is ideal for sealing components like valve covers, oil pans, intake manifolds, timing covers, and differential housings. It’s beneficial in areas prone to oil leaks or where high temperatures demand a durable, formed-in-place gasket.
2. Preparation of the Work Area and Conditions
Environmental Conditions
Applying Permatex Ultra Black requires a clean, dry, and ventilated workspace. The ideal temperature range is 50°F–100°F (10°C–38°C).
High humidity or moisture can interfere with curing, so avoid working in damp conditions. A controlled environment ensures the sealant adheres appropriately and cures evenly.
Surface Cleanliness
Start by removing any remnants of old gaskets using a scraper or plastic razor blade. Clean the surface thoroughly with a brake cleaner or acetone to remove oils, grease, and coolant residues.
Wipe the area dry with a lint-free cloth to ensure no contaminants remain, as even tiny particles can weaken the bond.
Surface Condition
Check that the mating surfaces are smooth and free from corrosion. If the parts have been machined, verify that no burrs or irregularities are present, as these can create gaps that compromise the seal. Taking time to prep the surface properly is key to a long-lasting repair.
3. Product Handling and Dispensing
Tube Preparation
Before dispensing the sealant, remove the cap and pierce the inner foil seal using the pointed end of the cap or a clean tool. Attach the nozzle and cut the tip to your desired bead size.
A bead size between 1/8″ and 1/4″ (3–6 mm) works best for most applications. Match the bead size to the flange width to avoid excessive squeeze-out.
Bead Consistency
Apply a steady, continuous bead of sealant along the mating surface. Maintain even pressure on the tube to prevent gaps or inconsistent application. Move slowly for parts with irregular surfaces to ensure the sealant fully adheres to the contours.
4. Application Techniques
Single-Surface Application
Apply the sealant to one mating surface only. Run the bead around the perimeter of the flange, ensuring it encircles all bolt holes.
Position the bead approximately 1/8″–1/4″ (3–6 mm) inboard from the bolt holes to prevent excess sealant from extruding into internal passages. This technique minimizes the risk of contamination.
Thickness Control
A 1/8″ (3 mm) bead is sufficient for most applications. However, the thickness can be adjusted based on the component gap and manufacturer specifications.
Avoid overapplying sealant, as too much material can interfere with the bolt’s clamping force or break off into internal engine passages.
Time Constraints
Once applied, the sealant must be assembled within 5–10 minutes to ensure it bonds before skinning over. If the sealant dries before assembly, remove it and reapply fresh material.
5. Assembly and Fastening Procedures
Part Alignment
Align the components carefully before assembly. Avoid sliding or shifting the parts once they’re in contact, as this can create air pockets or uneven distribution of the sealant.
Bolt Installation
Install bolts hand-tight in a crisscross pattern to distribute pressure evenly across the surface. Tighten bolts to about half their final torque value initially, then perform a second pass to achieve full torque.
Refer to OEM specifications for exact torque requirements, as over-tightening can squeeze out excess sealant and weaken the seal.
Bolt Recheck
After the initial torque sequence, recheck the bolt tightness if recommended. This step ensures the sealant compresses evenly as it sets, reducing the risk of leaks.
✔ Non-Corrosive & Sensor-Safe – Specially formulated for superior adhesion to oily surfaces, safe for modern engine sensors.
✔ Exceptional Fluid Resistance – Withstands engine oil, gear lube, transmission fluid, and coolant for a long-lasting, leak-proof seal.
✔ High Flex & Versatile Use – Ideal for replacing pre-cut gaskets or used as a sealant for tight, flexible sealing in demanding applications.
✔ Extreme Durability – Resists aging, shrinking, cracking, and thermal cycling with a working temp range of -65°F to 500°F.
✔ Ideal for Automotive Sealing Jobs – Perfect for valve covers, oil pans, timing covers, transmission pans, and more.
6. Curing and Post-Application Guidelines
Skin-Over Time
Permatex Ultra Black begins to skin over within a few minutes. To maintain the bead’s integrity, avoid disturbing the joint during this phase.
Initial Set Time
The sealant achieves an initial set within 1 hour. During this time, avoid applying pressure or vibration to the components to allow the seal to stabilize.
Full Cure Time
Full curing takes approximately 24 hours at room temperature, though this may vary slightly based on ambient conditions and bead thickness. Once cured, the sealant withstands intermittent operating temperatures up to 500°F (260°C) and resists automotive fluids.
7. Inspection and Verification
Visual Check
Inspect the joint for a uniform squeeze-out along the flange edges. A consistent bead indicates proper compression and seal integrity.
Leak Test (Optional)
Perform a leak test after the recommended cure time for critical components like oil pans. Run the engine briefly and check for any signs of seepage around the sealed area.
Rework
If a leak or improper bead formation is detected, disassemble the parts, clean thoroughly, and repeat the application process using a fresh sealant.
8. Compatibility and Limitations
Permatex Ultra Black is compatible with various automotive fluids, including engine oil, coolants, and synthetic lubricants. It adheres well to materials like cast iron, steel, aluminum, and certain automotive-grade plastics.
However, it’s unsuitable for applications involving continuous exposure to gasoline or high-pressure sealing surfaces requiring rigid gaskets, such as cylinder heads.
Final Thoughts
Achieving a reliable seal with Permatex Ultra Black requires attention to detail, from surface preparation to final assembly.
By following these steps, you can ensure a long-lasting and leak-free repair, whether working on an oil pan or a valve cover. With proper application and curing, this gasket maker delivers the durability and performance your engine needs.
Rebuilt 3.8 l Ford V6 4 days ago silicone has not set up at all very disappointed
Hi Lyn,
That’s really frustrating—after four days, it should’ve cured. Could be the product, surface prep, or even humidity. Sorry you’re dealing with that.