ULTIMATE BLACK GASKET MAKER & SEALANT
ULTIMATE BLACK GASKET MAKER & SEALANT
ULTIMATE BLACK GASKET MAKER & SEALANT
SKU: 32329

ULTIMATE BLACK GASKET MAKER & SEALANT

$7.99

Attributes

Oil Resistant
Low Odor
High Temperature
Sensor Safe
Water Resistant

Use On

Automotive
Metal

Product Details

J-B Weld Ultimate Black Gasket Maker and Sealant is an RTV (Room Temperature Vulcanized) Silicone gasketing material designed for use in mechanical assemblies where maximum petroleum and oil resistance is required. Upon curing, which occurs when the product is exposed to the moisture in air, the silicone forms a tough, waterproof, gasket and seal on most surfaces. It will not shrink or crack, resists oil and petroleum products, resists weathering, is sensor safe, has good temperature resistance up to 700°F intermittent and is great for many automotive applications.

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Product Attributes

Set Time
1 Hour
Dry Color
Black

Surfaces

Automotive
Metal

How to Use

Prepare

For best results, clean and dry surface area

Apply

Apply even, continuous ¼ inch bead of Silicone to one surface area. Surround all bolt holes with Silicone.

Assemble

Reconnect parts while Silicone is wet.

Secure

Hand tighten until Silicone begins to squeeze out.

Dry

Allow drying for 1 hour and then tighten an additional ½ turn.

Finish

Scrape or cut away excess cured sealant. Silicone will fully cure in 24 hours.

Frequently Asked Questions

What are the continuous and intermittent temperature ratings for Ultimate Black?

J-B Weld rates Ultimate Black at 500 F continuous and 700 F intermittent. Some older packaging printed only the 700 F figure on the front and 500 F on the back, which is the source of the confusion; the correct reading is 500 F sustained with short excursions to 700 F. For genuinely high-heat exhaust work, use Ultimate Copper 32325 instead.

Is Ultimate Black the right choice for oil leaks?

Yes. It is the most oil and petroleum resistant silicone in the J-B Weld line and is the recommended choice for oil pans, valve covers, timing covers, differential and transfer case covers, and engine case seams. It is not resistant to liquid gasoline, which dissolves all silicones, although incidental fuel vapor downstream of a carburetor is tolerated.

How long should Ultimate Black cure before I torque the bolts and start the engine?

Set time is one hour and full cure is 24 hours. For engine work, wait a minimum of 12 hours before letting the engine idle, and keep the joint completely oil-free during application and for roughly 12 hours afterward. Assemble and snug the fasteners while the bead is fresh, then bring them to final torque once the silicone has skinned over.

Can I use Ultimate Black on top of an existing paper, cork, or rubber gasket?

No. J-B Weld's position is that RTV silicone forms the gasket itself and should not be used in combination with one. Never put silicone on a rubber gasket, and use a purpose-made gasket dressing on paper or cork. On transmission pans in particular, keep the bead thin, because excess silicone can squeeze inside and reach the valve body, causing shift problems.

Is Ultimate Black sensor safe and low odor?

Yes. It is a neutral-cure oxime silicone, so it does not release the acetic acid and vinegar odor that acid-cure sealants give off, and J-B Weld lists it as sensor safe for use near oxygen sensors and other engine sensors. The neutral chemistry also makes it gentler on aluminum castings and painted surfaces than an acetoxy silicone.

How do I remove cured Ultimate Black when I service the part again?

It cures to a rubbery consistency rather than going hard, so it splits at the joint and cuts away easily with a razor or plastic scraper. Pare off the bulk, then soften and wipe the residue with a solvent such as acetone or brake cleaner before you reseal. Bring both flanges back to clean, dry, oil-free bare metal before applying a new bead.

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