For 1990-2009 cars

# BASECOAT/CLEARCOAT REPAIR SYSTEMS

#### VEHICLES AFFECTED: 1985 'M' Vans

The repair systems contained in this bulletin are recommended as a guide when repairing the basecoat/clearcoat exterior finish on the 'M' Van. Repair systems used on vehicles without the basecoat/clearcoat finish will not work on the 'M' Van.

Following are procedures that outline a method for making partial and full panel repairs on nonflexible parts and full panel repairs on flexible parts.

#### Nonflexible Panel Repair System

#### Procedure - Spot or Repair Blending (Figure 1)

#### Basecoat

1. Wash with a mild detergent and water to remove any water soluble contaminants, then clean with a wax and grease removing solvent to remove any tar, silicone or other road film not removed with the detergent wash.

2. Repair and featheredge damaged area(s) as required.

3. If substrate is metal, treat surface with a metal conditioner and conversion coating according to label directions and allow to dry thoroughly. Apply primer-surfacer to repair and featheredge damaged area(s) as required. Allow to dry 20-30 minutes before sanding.

4. Using wet or dry No. 400 grit sandpaper or finer, sand entire area(s) to be refinished with the basecoat colour. Areas to be clear coated only, should be wet sanded with No. 600 or finer sandpaper.

5. Reclean panel(s) with wax and grease removing solvent and then tack wipe.

6. Apply one coat of an 'adhesion promoter' over the entire area(s) to be painted. Allow a minimum of 30 minutes dry time.

7. The base colour should be reduced 150-200% with an extra-slow drying lacquer solvent. The viscosity of the reduced base colour is very important in order to match the O.E.M. (original equipment manufacturer) finish. The best way of checking the viscosity of a reduced paint material is with a Zahn No. 2 paint viscosity cup or its equivalent.

Temperature influences viscosity directly. If a cold can of paint is brought into an average temperature room (65-70 degrees), it will be thicker and more viscous. Adding solvent to make the paint sprayable is not always the best action. The paint should be allowed to reach workable or average room temperatures. Follow manufacturer's recommended paint viscosity cup reading for their specific material.

8. Apply two or three medium-wet coats of base colour. Note: Apply only the number of coats necessary to achieve full hiding. Spray at 35-45 lbs. air pressure at the gun. Allow the final coat to flash approximately five minutes before applying the final coat of base colour, allow it to dry for 20 minutes before applying the clear coat.

9. If base coat must be sanded, proceed as follows:

a. Allow base colour to dry.

b.Sand with ultra-fine wet-or-dry sandpaper to remove the imperfection(s).

c. Reclean and tack wipe the repair area(s).

d. Apply one more additional coat of base colour.

e. Allow to dry 20 minutes before applying the clear coat.

#### Clear Coat

#### Lacquer Clearcoat

1. Reduce clearcoat 125-150% with an extra-slow drying lacquer thinner to the recommended paint viscosity cup read of the manufacturer of the paint you are using.

2. Spray two medium-wet coats of reduced clear at 35-45 lbs. air pressure at the gun. Allow first coat to flash completely before applying the second coat. At least two coats must be used. Additional coats may be applied if desired. If If additional leveling is desired a final coat of premixed mist-coat material (clear acrylic and thinner) can be sprayed at 20 lbs. air pressure at the gun.

3. Allow overnight dry or longer, then, rub out using a light-cutting hand or machine polishing compound.

B. Enamel Clearcoat ----------------

#### CAUTION:

There are a number of paint systems available for service use: however, many require additives containing isocyanates. It is essential that all recommendations and warnings listed on the container label for materials selected be followed.

It is mandatory that adequate respiratory protection be worn. Examples of such protection are: 3-M models No. 6984 and No. 6986 disposable respirators.

Such protection should be worn during the entire painting process. Persons with respiratory problems, or those allergic to isocyanates must not be exposed to isocyanate vapors or spray mist.

1. Following paint manufacturers label directions, activate the Polyurethane Enamel Clearcoat material. Mix material thoroughly. Pot life of activated mixture is approximately eight (8) hours.

2. Some activated Polyurethane Enamel Clearcoat materials are ready to spray as packaged under normal conditions. As conditions vary, to enhance flow out and leveling, up to 10% more than the specified enamel reducer may be added to the activated clearcoat mixture. Check the viscosity of the activated mixture with a Zahn No. 2 paint viscosity cup or its equivalent. Follow the paint manufacturer's labeled recommendations for paint viscosity cup reading.

3. Spray two medium coats of activated clearcoat material at 50 lbs. air pressure at the gun over entire area(s) to be refinished. For panel repairs, allow 15-20 minutes dry time between coats. For overall refinishing, apply first coat, allow to flash, then apply second coat. Spray medium-wet coats of clear coat material to reduce surface texture (orange peel) and provide optimum appearance. Allow to cure overnight.

#### Flexible Panel Repair System

#### Procedure - Full Panel

Full panel repairs must be performed, spot repairs are not recommended.

#### CAUTION:

There are a number of flexible paint systems available for service use: however, many required additives containing isocyanates. It is essential that all recommendations and warnings listed on the container label for materials selected be followed.

It is mandatory that adequate respiratory protection be worn. Examples of such protection area: 3-M models No. 6984 and No. 6986 disposable respirators.

Such protection should be worn during the entire paint process. persons with respiratory problems, or those allergic to isocyanates must not be exposed to isocyanate vapors or spray mist.

1. Flexible Undercoat Requirements

If the part to be painted is a replacement, it will be factory primed with an elastomeric enamel-based primer. As long as the original primer is not scratched exposing the plastic substrate, all that is required is to solvent clean, sand with No. 400 paper or a red 'Scotch-Brite' pad, reclean and apply elastomeric colour.

However, if the plastic substrate is exposed or the part is repaired with flexible filler material, a flexible primer surfacer must be used to provide the filling properties required. This is to prevent a 'bull's-eye' condition or highlighting of the bare substrate or filler repair after colour is applied.

Prepare flexible primer surfacer as follows:

a. Clean the entire part with a wax, grease and silicone removing solvent applied with a water dampened cloth. Wipe dry.

#### NOTE: The step above begins to prepare the entire part for colour coats. Spot repair is not recommended because dry spray at the blend area of applied elastomeric colour does not 'wet out' satisfactorily.

b. Featheredge the scuff or filler repair with No. 320 sandpaper, blow off dust and tack wipe.

c. Mix and apply four medium dry coats of flexible primer surfacer. Follow manufacturer's instructions for specific mix ratios and additives.

#### NOTE: Use a fact evaporting thinner as recommended to reduce the primer-surfacer and do not apply excessively wet coats. Bare flexible plastic surface and/or flexible filler materials have a tendency to swell from thinner absorption resulting in a reduce the primer-surfacer visible or 'highlighted' repair.

d. Allow to dry at least one hour and block sand with No. 400 sandpaper. Sand the entire part with No. 400 sandpaper or 'red' 'Scotch-Brite' pad to remove all gloss in preparation for colour application.

When paints are modified with a flex additive, the possibility of mixture 'pot life' exists; therefore, spray equipment should be emptied and flushed immediately after use.

2. Body Colour With Flexible Additive Systems -------------------------------------------

There are several flexibletopcoat systems available for the painter's selections; in most cases, it is a matter of personal preference. Basecoat/clearcoat material can be either enamel or lacquer-based. Some manufacturers do not recommended the use of flex additives in their basecolour material, but do recommend its use for their lacquer and enamel clear coats.

a. Thoroughly sand the entire part with No. 400 sandpaper or red 'Scotch-Brite' pad to remove all gloss. Reclean.

b. Mix the base colour, flexible additive, if recommended, and thinner. Follow manufacturer's label instructions.

c. Apply a sufficient number of coats to achieve complete hiding and colour match. Allow flash time between coats.

d. Allow the base colour coat to dry 30-60 minutes before applying the clearcoat. Do not sand the base coat before applying the clearcoat.

#### NOTE: If sanding of the base coat is necessary to remove imperfections, such as dirt or sags, sand with No. 400 grit or finer sandpaper, reclean the area(s). Apply one additional coat of base material and let dry.

3. Clearcoat Application ---------------------

a. Mix and reduce clear coat (lacquer or enamel) mdterial as per label instructions.

#### NOTE: Use flex additive if recommended by paint source.

b. Strain the mixture and apply 2-3 coats with 35-40 lbs. air pressure at the gun.

c. Allow each coat to flash completely before applying the next coat. Allow at least 4 hours air dry time or force dry for 30 minutes with a heat lamp at 180 degrees Fahrenheit before putting into service.

#### NOTE: Compounding is not necessary when a flexible additive is used in the top coat paint material. The mixture will dry with acceptable gloss.

Compounding dulls the gloss of elastomeric finishes causing a flat appearance. The finish cannot be brought back to the same gloss level without applying more paint.

#### Clearcoat

A. Lacquer Clearcoat -----------------

1. Reduce clearcoaL 125-150% With an extra-slow drying lacquer thinner to the recommended paint viscosity cup reading of the manufacturer who's paint product you are using.

2. Spray at least two medium-wet coats of clear at 35-40 lbs. air pressure at the gun. More may be desired. Spray first coat beyond base colour coat and allow to flash for approximately 5-10 minutes. Spray each additional coat of clear slightly beyond the previously applied clearcoat. Allow flash time between coats. After the final coat of clear is applied, apply a mist-coat (clear acrylic and- thinner) to melt in overspray. Stay within the applied 'adhesion promoter' with all spray operations. Allow the repair to dry overnight, then, rub out with a light-cutting hand or machine polishing compound.

B. Enamel Clearcoat ----------------

#### CAUTION:

There are a number of paint systems available for service use: however, many require additives containing isocyanates. It is essential that all recomLendations and warnings listed on the container label for materials selected be followed.

It is mandatory that adequate respiratory protection be worn. Examples of such protection are: 3-M models No. 6984 and No. 6986 disposable respirators.

Such protection should be worn during the entire painting process. Persons with respiratory problems, or those allergic to is ocyanates must not exposed to isocyanate vapors or spray mist.

1. Following paint manufacturer's label directions, activate the Polyurethane Enamel Clearcoat material. Mix material thoroughly. Pot life of activated mixture is approximately eight (8) hours.

2. Reduce clearcoat per label directions. Some activated Polyurethane Enamel Clearcoat materials are ready to spray as packaged under normal conditions. As conditions vary, to enhance flow out and leveling up to 10% more than the specified enamel reducer may be added to the activated clearcoat mixture. Check the viscosity of the activated mixture with a Zahn No. 2 Paint viscosity cup or its equivalent. Follow the paint manufacturer's labeled recommendations for paint visicosity cup reading.

3. Using 50 lbs. air pressure at the gun, spray two medium-wet coats of enamel cleracoat mixture. Allow first coat to set-up for 15-20 minutes before applying the second final coat. Allow to cure overnight.

Clean spray painting equipment with lacquer thinner immediately after use.

#### Procedure - Full Panel Repair (Figure 2)

#### Basecoat

1. Wash with a mild detergent and water to remove any water soluable contaminates, then clean with a wax and grease removing solvent to remove any tar, silicone or other road film not removed with the detergent wash.

2. Sand the complete panel(s) with 400 grit or finer wet-or-dry sandpaper. Repair and featheredge damaged areas as required. Treat all bare metal with recommended metal conditioner and conversion coating. Follow manufacturer's label directions.

3. Apply primer-surfacer to all bare metal areas. Keep primer-surfacer within the damaged area(s). Allow to dry 20-30 minutes before sanding.

4. Using No. 400 grit or finer sandpaper, sand the primer-surfacer to level the imperfection.

5. Reclean panel(s) with wax and grease removing solvent and then tack wipe.

#### Spot Repair with Lacquer Clear Coat - (Figure 1)

1. Wet sand area to be primed and colour coated with 400 grit or finer.

2. Wet sand area to be clear coated only, with 600 grit or finer.

3. Apply adhesion promoter over and beyond sanded areas.

4. Apply base colour coat as per label directions.

5. Apply lacquar clearcoat beyond base colour coat but within adhesion promoter. Allow to dry overnight and compound.

#### Panel Repair With Enamel Clear Coat - (Figure 2)

1. Wet sand area to be primed and colour with 400 grit or finer.

2. Wet sand entire area to be clear coated with 600 grit or finer.

3. Apply an adhesion promoter over entire area to be colour coated and clear coated.

4. Apply base colourcoat over repair only as per label directions.

5. Apply enamel clearcoat over entire panel as per label directions.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.