Ls400 Rear Wheel Arch Liners

[Colin M]

Although Lexus fitted plastic liners inside the front wheel
arches, which provide good protection from road grit etc, they did not fit them
inside the rear wheel arches. Here you have to rely on the underseal coating
for protection. Although this does provide good protection generally, the
coating is thin in the area just above the wheel arch lip, where rust can set
in. It had on my 1996 Mk 3 car and, having addressed the rust issues, I have
now fitted into the rear wheel arches a pair of front liners from a scrap LS400
to give a better level of protection.

I have set out below what this involved and I have made the
fitting so that it can be reversed at any time in the future, without any signs
of the fitting having been made i.e. no holes drilled in the bodywork. The
following steps set out how it is done:

1 Take the relevant liner for the side of the car on which you are going to start (I
started with the Near Side) and cut off two sections of the liner before you
start trying to fit it. One is the horizontal section at the front that fits
under the front bumper and the other is a small strip on the inside edge at the
front of the wheel arch (because, when fitting in the rear arch, this catches
the tie-rod and prevents the liner being moved into place). I used metal
cutting shears to do the cutting, although a sharp knife should do just as
well. Photo 1 shows the complete OS liner and Photo 2 the NS liner with these
two sections cut off.

2 Remove the 5 allen head screws which hold the mudflap in place and remove the mudflap. Note that the two in the middle row are longer than the top one and two bottom ones.
Position the liner loosely around the inner edge of the wheel arch lip and you
should find that the two middle screw holes and the inner bottom screw hole are
covered by the liner but the outer bottom screw hole for the mudflap is still
just visible. Put a penny/mudguard/repair washer on the allen head screw for
this hole and screw tit into the hole so that enough of the washer projects
over the liner to hold it in place. Before doing so, you need to trim about one
inch in length off the small lip (1/4 inch) that projects backwards from the
rear of the liner. Leave the rest of the lip on and this will slot between the
rear lower body panel and the mudflap. If you do not remove part of the lip, it
will not fit flush.

3 With the rear of the liner (temporarily) held in place with the allen screw and washer,
you can then fit the outer edge of the liner around the inner wheel arch lip.
The liner will more or less follow the profile of the arch until you come to
the front section and here the outer edge of the liner will need trimming off
so that it fits snugly inside the wheel arch lip. This is best done by cutting
off several small sections and progressively reducing the profile of the outer
edge until it is a good fit.

4 Clamp the bottom inner edges of the liner to the bottom edge of the inside of the wheel
arch using mudflap clamps which have a screw that can be tightened to hold the
clamp in place. These can be bought from local motor accessory shops or off
eBay. They are about 50p per clamp, usually sold in packs of 4.

5 Remove the four screws that hold the black plastic wheel arch trim to the outside of the
wheel arch lip. This is so that plastic strips at one end can be held in place
between the outside of the wheel arch lip and the inside of the black plastic
wheel arch trim when the trim is reattached, with the other end fastened to the
edge of the plastic arch liner. Three plastic strips were fitted, one at each
screw hole except the rearmost one, to enable the wheel arch liner to be
fastened around its outer edge. One could be fitted in the rearmost screw hole
as well but shortly below this is the top allen screw for the mudflap which
will pass through the plastic arch liner to hold it in place at this point when
the mudflap is refitted. A plastic strip is not therefore really needed here.

6 The plastic strips, each about one inch wide, can be cut from the horizontal section that
you removed from the front of the wheel arch liner at the start (see 1 above).
These need to be cut from the section where there is a right angle in the
plastic – see Photo 3. The inside of the right angle is placed on the inside
edge of the wheel arch, so that one side projects out over the wheel arch lip
and the other projects upwards onto the inside of the wheel arch.

7 The method of fitting the plastic strip between the wheel arch lip and trim is as follows.
You will see that the plastic inserts into which the screws go have a square
shaped head which sits slightly proud of the wheel arch lip. If a hole is
drilled in a piece of plastic and the hole is made into a square using a small
square file, so that the square is slightly larger than the square shaped head,
the plastic can be placed over the square shaped head and will be held in place
between the wheel arch lip and trim when the trim is reattached. The trim will
reseat properly provided the square shaped hole in the plastic is big enough to
clear the square shaped head. When the square hole in the plastic is placed
over the square shaped head, trim off any excess plastic extending beyond the
wheel arch lip. This should leave about one eighth of an inch of plastic at the
outside edge of the strip before the square hole starts, ensuring that the edge
does not project beyond the trim.

8 The method of fitting the plastic strip to the outer edge of the wheel arch liner is as
follows, using a spire clip, screw and penny washer. Push the spire clip onto
the edge of the wheel arch liner inside the wheel arch so that it aligns with
the screw hole in the black plastic wheel arch trim. Push a bradawl through the
hole in the spire clip to enable the screw to go through it. Position the
square hole in the plastic strip over the square shaped head. Fix in place
using the screw for the square shaped head, with a washer on the screw so that
it holds the plastic strip firmly in place (using a washer is easier than
refitting the black plastic wheel arch trim). Then work out where you need to
drill a hole in the plastic strip so that when the screw (with penny washer) is
pushed through it the screw end will slot into the spire clip hole. Drawing a
horizontal and vertical pencil line from the bradawl hole, so that the lines
project beyond the plastic strip will give you a good idea where the hole needs
to go. Drill the hole so that there is sufficient clearance for the screw to go
through it.

9 A completed plastic strip should look something like Photo 4. This shows the square hole that
fits over the square shaped head (with the screw that goes into the head below),
the hole at the other end for the screw and penny washer, and the spire clip
that fits on the edge of the plastic liner. The screw is 7 mm hexhead, rather
than cross or flat head screwdriver, but any type of screw can be used. The
spire clip has the screw hole inset about half an inch, rather than close to
the edge of the clip.

10 Make and fit three plastic strips, as above, and then refit the black plastic wheel arch
trim, making sure that it seats properly.

11 Remove the allen screw and washer which have been temporarily holding the rear of the
wheel arch liner in place (see 3 above). Place the mudflap in position and push
a bradawl through each of the screw holes in the mudflap so that you know where
holes need to be drilled in the rear of the wheel arch liner to allow the
screws to go through to their screw holes. Remove the mudflap and drill the
holes in wheel arch liner, allowing sufficient clearance for the screws. Refit
the mudflap and screw the five allen head screws back into place.

12 Finally, make any further trimming of material from the wheel arch liner as necessary, using
a sharp knife. Photo 5 shows the wheel arch liner as finally fitted.

I hope the above guide is useful if any of you are thinking
of going down the same route.

Cheers,

Colin

[steve2006]

A very decent and detailed tutorial and something I for one had never considered doing.

Thank you for taking the time and trouble of posting this.

The only concern I would have is if muck gets trapped behind the liner and causes rust problems in the future.

I have always cleaned my arches after every winter and reapplied sealant if required and so far have had no rust problems.

The plastic trim around the arch is also easily removed so the crud can be washed off this and the arch.

[Bluesbreaker]

Well Sir,I have to take off my hat to you,that was one of the most comprehensive,detailed,explanations,I think I have ever seen on this Forum,now you've got me wanting to get under my rear wheel-arches,at the earliest opportunity .....

[Colin M]

Thanks Steve and Iain for your comments.

I share your concern, Steve, about mud getting trapped and, like you, I always clean the arches out after each winter.

I think there will be enough of a gap at various points where the liner sits around the wheel arch lip to allow any mud to escape, but time will tell and I will be keeping an eye on things.

As you say, the plastic trim around the arch is easily removed and when it is the edge of the liner can be levered forward a bit with a screwdriver to see whether any mud is trapped behind.

Cheers

Colin

[steve2006]

I wondered what to do with all the plastics from my scrap LS, I can now make use of the front arches.