1991 BMW 5 SERIES Warm up

it to the approximate size and shape required,
then pull off the backing paper (if used) and
stick the tape over the hole; it can be
overlapped if the thickness of one piece is
insufficient. Burnish down the edges of the
tape with the handle of a screwdriver or
similar, to ensure that the tape is securely
attached to the metal underneath.
Bodywork repairs - filling and
respraying
Before using this Section, see the Sections
on dent, deep scratch, rust holes and gash
repairs.
Many types of bodyfiller are available, but
generally speaking, those proprietary kits
which contain a tin of filler paste and a tube of
resin hardener are best for this type of repair. A
wide, flexible plastic or nylon applicator will be
found invaluable for imparting a smooth and
well-contoured finish to the surface of the filler.
Mix up a little filler on a clean piece of card
or board - measure the hardener carefully
(follow the maker’s instructions on the pack),
otherwise the filler will set too rapidly or too
slowly. Using the applicator, apply the filler
paste to the prepared area; draw the
applicator across the surface of the filler to
achieve the correct contour and to level the
surface. As soon as a contour that
approximates to the correct one is achieved,
stop working the paste - if you carry on too
long, the paste will become sticky and begin
to “pick-up” on the applicator. Continue to
add thin layers of filler paste at 20-minute
intervals, until the level of the filler is just
proud of the surrounding bodywork.
Once the filler has hardened, the excess
can be removed using a metal plane or file.
From then on, progressively-finer grades of
abrasive paper should be used, starting with a
40-grade production paper, and finishing with
a 400-grade wet-and-dry paper. Always wrap
the abrasive paper around a flat rubber, cork,
or wooden block - otherwise the surface of
the filler will not be completely flat. During the
smoothing of the filler surface, the wet-and-
dry paper should be periodically rinsed in
water. This will ensure that a very smooth
finish is imparted to the filler at the final stage.
At this stage, the “dent” should be
surrounded by a ring of bare metal, which in
turn should be encircled by the finely
“feathered” edge of the good paintwork.
Rinse the repair area with clean water, until all
of the dust produced by the rubbing-down
operation has gone.
Spray the whole area with a light coat of
primer - this will show up any imperfections in
the surface of the filler. Repair these
imperfections with fresh filler paste or
bodystopper, and once more smooth the
surface with abrasive paper. Repeat this
spray-and-repair procedure until you are
satisfied that the surface of the filler, and the
feathered edge of the paintwork, are perfect.
Clean the repair area with clean water, and
allow to dry fully.The repair area is now ready for final
spraying. Paint spraying must be carried out
in a warm, dry, windless and dust-free
atmosphere. This condition can be created
artificially if you have access to a large indoor
working area, but if you are forced to work in
the open, you will have to pick your day very
carefully. If you are working indoors, dousing
the floor in the work area with water will help
to settle the dust which would otherwise be in
the atmosphere. If the repair area is confined
to one body panel, mask off the surrounding
panels; this will help to minimise the effects of
a slight mis-match in paint colours. Bodywork
fittings (eg chrome strips, door handles etc)
will also need to be masked off. Use genuine
masking tape, and several thicknesses of
newspaper, for the masking operations.
Before commencing to spray, agitate the
aerosol can thoroughly, then spray a test area
(an old tin, or similar) until the technique is
mastered. Cover the repair area with a thick
coat of primer; the thickness should be built
up using several thin layers of paint, rather
than one thick one. Using 400-grade wet-and-
dry paper, rub down the surface of the primer
until it is really smooth. While doing this, the
work area should be thoroughly doused with
water, and the wet-and-dry paper periodically
rinsed in water. Allow to dry before spraying
on more paint.
Spray on the top coat, again building up the
thickness by using several thin layers of paint.
Start spraying at one edge of the repair area,
and then, using a side-to-side motion, work
until the whole repair area and about 2 inches
of the surrounding original paintwork is
covered. Remove all masking material 10 to
15 minutes after spraying on the final coat of
paint.
Allow the new paint at least two weeks to
harden, then, using a paintwork renovator, or
a very fine cutting paste, blend the edges of
the paint into the existing paintwork. Finally,
apply wax polish.
Plastic components
With the use of more and more plastic body
components by the vehicle manufacturers (eg
bumpers. spoilers, and in some cases major
body panels), rectification of more serious
damage to such items has become a matter
of either entrusting repair work to a specialist
in this field, or renewing complete
components. Repair of such damage by the
DIY owner is not really feasible, owing to the
cost of the equipment and materials required
for effecting such repairs. The basic technique
involves making a groove along the line of the
crack in the plastic, using a rotary burr in a
power drill. The damaged part is then weldedback together, using a hot-air gun to heat up
and fuse a plastic filler rod into the groove.
Any excess plastic is then removed, and the
area rubbed down to a smooth finish. It is
important that a filler rod of the correct plastic
is used, as body components can be made of
a variety of different types (eg polycarbonate,
ABS, polypropylene).
Damage of a less serious nature (abrasions,
minor cracks etc) can be repaired by the DIY
owner using a two-part epoxy filler repair
material. Once mixed in equal proportions,
this is used in similar fashion to the bodywork
filler used on metal panels. The filler is usually
cured in twenty to thirty minutes, ready for
sanding and painting.
If the owner is renewing a complete
component himself, or if he has repaired it
with epoxy filler, he will be left with the
problem of finding a suitable paint for finishing
which is compatible with the type of plastic
used. At one time, the use of a universal paint
was not possible, owing to the complex range
of plastics encountered in body component
applications. Standard paints, generally
speaking, will not bond to plastic or rubber
satisfactorily. However, it is now possible to
obtain a plastic body parts finishing kit which
consists of a pre-primer treatment, a primer
and coloured top coat. Full instructions are
normally supplied with a kit, but basically, the
method of use is to first apply the pre-primer
to the component concerned, and allow it to
dry for up to 30 minutes. Then the primer is
applied, and left to dry for about an hour
before finally applying the special-coloured
top coat. The result is a correctly-coloured
component, where the paint will flex with the
plastic or rubber, a property that standard
paint does not normally possess.
6 Bodywork repair-
major damage
5
1Major damage must be repaired by a
qualified bodywork repair specialist, or
preferably by a BMW dealer. Specialised
equipment is required to do the job properly.
2If the damage is extensive, the bodyshell
must be checked for proper alignment, or the
vehicle’s handling characteristics may be
adversely affected and other components
may wear at an accelerated rate.
3Due to the fact that all of the major body
components (bonnet, wings, etc.) are
separate units, any seriously damaged
components should be replaced with new
ones rather than repaired.
Bodywork and fittings 11•3
11
If bodystopper is used, it can
be mixed with cellulose
thinners to form a really thin
paste which is ideal for filling
small holes
Sometimes bodywork
components can be found in
a scrapyard that specialises
in used vehicle components,
often at a considerable saving over the
cost of new parts.