RTV sealant depends greatly on adhesion to the mating parts in order to form and maintain a robust sealed joint. As with any adhesion system, proper surface preparation of the bonded parts is extremely important to ensure good adhesion over the life of the product.

Abrasive pads, wire wheels and bristle discs can remove enough metal to affect the engine front cover, cylinder head, engine block, oil pan rail, and intake manifold runner surface flatness, which can then result in engine coolant leaks, engine oil leaks and air leaks. It takes about 15 seconds to remove 0.203 mm  (0.008 in) of metal with an abrasive pad.

Abrasive pads, wire wheels and bristle discs used with high speed grinders produce airborne debris that can travel throughout the shop contaminating other work being performed outside of the immediate work area.

When cleaning engine gasket sealing surfaces and/or cleaning parts from an engine that are to be reused, surface conditioning discs, typically constructed of woven fiber or molded bristles that contain abrasives, such as a high amount of aluminum oxide, should NOT be used. The use of such surface conditioning discs dislodges aluminum oxide from the disk and metal component particles, which can lead to premature engine bearing failure. The presence of aluminum oxide in engine oil has been shown to cause premature engine bearing failure. In some cases, this failure occurs in as little as 1,600 km (1,000 mi) or less after the repair has been made.

Surface conditioning discs may grind the component material and embed it into the disc. This can result when more aggressive grinding of the gasket surface takes place.

General Motors strongly recommends using a plastic razor blade, plastic gasket scraper, a wood scraper or a non-metallic scraper to remove all sealer/gasket material on the surface of engine components that are to be reused. Do not use any other method or technique to remove the sealant or the gasket material from a part.

• Do not gouge or scratch any engine sealing surface during the cleaning process.
• It is not necessary to remove every speck of the old sealer.

To remove the old RTV sealant from the sealing surface, spray GM Low VOC Cleaner or an equivalent, on the mating surfaces and allow it to soak to loosen the old gasket material. Use care to avoid getting GM Low VOC Cleaner in any area other than the mating surface to be cleaned.

Use a plastic razor blade, that mounts in a scraper device or a hand held plastic razor blade, to remove old RTV sealant from a sealing surface. Use a new blade for each corresponding engine component surface. Hold the blade as parallel to the flat surface as possible.

To properly clean the sealing surfaces prior to reassembly, spray GM Low VOC Cleaner on a folded lint free shop cloth. Wipe the mating surfaces on the engine and front cover and rotate the shop cloth until there are no more visible signs of contamination on the cloth.

After the final cleaning of the parts, allow up to 5 minutes for the components to dry before applying new RTV sealant.

This procedure is intended for use in the following operations:

• Building of engines in a manual low volume build process where the use of assembly lubricants and other typical conditions exist which may contaminate the component sealing surfaces in an RTV joint.
• Cleaning of surfaces contaminated with oil or other substance during the assembly operation as a special case event.

In the typical situation, both the part being assembled, and the assembly to which it is to be sealed will be cleaned. An example is an oil pan assembled to a block/front cover/rear cover assembly using an RTV seal applied to the pan or the block. Both the pan and the block assembly should be cleaned prior to RTV application.

Any loose gaskets that are part of the RTV joint should not be cleaned unless it is known that they have been contaminated during the build process. Examples of loose gaskets are intake side and end seals which contact RTV used to seal a T-joint.

Assemblies supplied to GM with gaskets in place should not be cleaned unless they are known to be contaminated during the build process. Examples are rocker/cam covers with press in place gaskets using RTV at corners or T-joints.

Use clean dry lint free cloths to wipe surface with approved solvent based cleaner. Examples are:

• GM Good Wrench Service Low VOC Brake Parts Cleaner
• AC Delco Non-Chlorinated Brake Parts Cleaner
• Loctite ODC –Free Cleaner & Degreaser

1. Identify the surfaces to which the RTV will come into contact in the assembled joint.
2. Using an approved solvent based cleaner, thoroughly soak an appropriate portion of a clean, dry cloth. Immediately wipe the surfaces with the cloth to remove any residue of oil, soap, etc.
3. Repeat step 2 using a clean portion of the cloth as many times as required until the cleanliness of the cloth after wiping the surface becomes constant in appearance. There is typically some discoloration of the cloth after wiping however a clean surface should produce the same level of discoloration with successive wiping with a clean cloth and solvent.
4. If crevices exist in the joint such that wiping the surface would not be sufficient to clean the crevice, the approved solvent based cleaner should be directly sprayed on the joint to ensure wetting of the surfaces and removal of the contaminant. DO NOT spray rubber components directly. Care must be used to avoid getting solvent in areas other than necessary to clean the joint. Then continue with step 3.
5. Allow the surfaces to dry for a minimum of 1 minute or longer if necessary for the solvent to evaporate from the surface.
6. Do not touch the cleaned surface with anything prior to RTV application.
7. The surface is now prepared for RTV application.

The following two major types of sealant are commonly used in engines:

• Room Temperature Vulcanizing (RTV)
• Anaerobic sealant, which include the following:
• Gasket Eliminator
• Pipe Sealant
• Threadlock

This type of sealant is used where two components, such as the intake manifold and the engine block, are assembled together.

Use the following information when using RTV sealant:

• Do not use RTV sealant in areas where extreme temperatures are expected. These areas include:
• The exhaust manifold
• The head gasket
• Any other surfaces where a different type of sealant is specified in the service procedure
• Do not use RTV sealant unless the ambient air temperature is at least 18°C (65°F) degrees or higher.
• Always follow all the safety recommendations and the directions that are on the RTV sealant container.
• Use a plastic or wood scraper in order to remove all the RTV sealant from the components.

Caution: Do not allow the RTV sealant to enter any blind threaded hole. RTV sealant that is allowed to enter a blind threaded hole can cause hydraulic lock of the fastener when the fastener is tightened. Hydraulic lock of a fastener can lead to damage to the fastener and/or the components. Hydraulic lock of a fastener can also prevent the proper clamping loads to be obtained when the fastener is tightened. Improper clamping loads can prevent proper sealing of the components allowing leakage to occur. Preventing proper fastener tightening can allow the components to loosen or separate leading to extensive engine damage.

• The surfaces to be sealed must be clean and dry.

Note: The bead size is critical and is easier to maintain consistency and application with a RTV dispensing tool. This also helps to eliminate waste.

• Use a RTV sealant bead size as specified in the service procedure.
• Apply the RTV sealant bead to the inside of any bolt holes areas.

Note: Do not wait for the RTV sealant to skin over.

• Assemble the components while the RTV sealant is still wet to the touch, within 10 minutes.

Note: Do not overtighten the fasteners.

• Tighten the fasteners in sequence, if specified, and to the proper torque specifications.

Anaerobic type gasket eliminator sealant cures in the absence of air. This type of sealant is used where two rigid parts, such as castings, are assembled together. When two rigid parts are disassembled and no sealant or gasket is readily noticeable, then the two parts were probably assembled using an anaerobic type gasket eliminator sealant.

Use the following information when using gasket eliminator sealant:

• Always follow all the safety recommendations and directions that are on the gasket eliminator sealant container.
• Apply a continuous bead of gasket eliminator sealant to one flange.
• The surfaces to be sealed must be clean and dry.

Caution: Do not allow the sealant to enter a blind hole. The sealant may prevent the fastener from achieving proper clamp load, cause component damage when the fastener is tightened, or lead to component failure.

• Do not allow the gasket eliminator sealed joint to cure more than 5 minutes before torquing to specification. This will result in an incorrect clamp load of assembled components.
• Do not overtighten the fasteners.
• Apply the gasket eliminator sealant evenly to get a uniform thickness of the gasket eliminator sealant on the sealing surface.
• Tighten the fasteners in sequence, if specified, and to the proper torque specifications.
• After properly tightening the fasteners, remove the excess gasket eliminator sealant from the outside of the joint.

Anaerobic type threadlock sealant cures in the absence of air. This type of sealant is used for threadlocking and sealing of bolts, fittings, nuts, and studs. This type of sealant cures only when confined between two close fitting metal surfaces.

Use the following information when using threadlock sealant:

• Always follow all safety recommendations and directions that are on the threadlock sealant container.
• The threaded surfaces to be sealed must be clean and dry.
• Apply the threadlock sealant as specified on the threadlock sealant container.

Note:

• Do not allow the threadlock sealant to cure more than 5 minutes before torquing to specification. This will result in an incorrect clamp load of assembled components.
• Do not overtighten the fasteners.

• Tighten the fasteners in sequence, if specified, and to the proper torque specifications.

Anaerobic type pipe sealant cures in the absence of air and remains pliable when cured. This type of sealant is used where two parts are assembled together and require a leak proof joint.

Use the following information when using pipe sealant:

• Do not use pipe sealant in areas where extreme temperatures are expected. These areas include:
• The exhaust manifold
• The head gasket
• Surfaces where a different sealant is specified
• Always follow all the safety recommendations and the directions that are on the pipe sealant container.
• The surfaces to be sealed must be clean and dry.
• Use a pipe sealant bead of the size or quantity as specified in the service procedure.

Caution: Do not allow the sealant to enter a blind hole. The sealant may prevent the fastener from achieving proper clamp load, cause component damage when the fastener is tightened, or lead to component failure.

• Apply the pipe sealant bead to the inside of any bolt hole areas.
• Apply a continuous bead of pipe sealant to one sealing surface.

Note: Do not overtighten the fasteners.

• Tighten the fasteners in sequence, if specified, and to the proper torque specifications.