REPAIRS - PAGE 9
THE ACHILLES HEEL – THOSE REAR ARCHES
There can’t be many of us lucky enough to avoid that dreaded
blistering paint on the rear wheel arches, it is enough to strike fear into the
heart of any owner and it seems to be the bane of the MKl! Once it starts it
really is a battle to slow the rust down, and the rust will win, it is only a
matter of how quickly.
Fibre glassing or patch welding are OK as short-term fixes, but it is more
than likely that the dreaded paint bubbling will reappear,(sooner rather than
later) - either around the repair edges or further around the arch. In other
words once the rust erupts at one point it is well on its way through in the
area around it.
This is due to the design of the arch - the time honoured double lip - ie
where inner and outer arches were set together and spot-welded. This can be seen
in the sketches that follow later. The hidden ledge and the inevitable gaps
between the spot welds form a cosy crevice for moisture, mud and salt - which is
the perfect cocktail for rust to form and spread outwards.
Without full wax undersealing - both ‘externally’ and internally between
the arch lips this design is very rust prone over time. Bearing in mind that
the the MKl is a mid-80’s car when full rustproofing was not that thorough, and
the usual car design life was 7 years, then such problems are inevitable.
It is no wonder that so many of us are facing this tricky problem - 80’s
design and time eventually take their toll.
That’s the bad news - the consolation is that many enthusiasts have ‘been
there before us’ - with equally good cars of an earlier vintage. They have over
time evolved techniques which are just as relevant to our MKls.
This is amply demonstrated by the following article - which has been kindly
written by the Technical Secretary of the MG ‘A’ Club - Geoff Barron.
The link is that Geoff has ‘had’ to do this work on a MKl due to his son's
purchase of one. He has very kindly sent me a comprehensive description plus
photos of the job method- credits are definitely due here to Geoff. (I can
personally vouch for having used the same procedure - albeit not on a MKl -
yet.) So, here is his article:-
My son recently decided to buy a proper car but lacking adequate funds
persuaded me to purchase an accident damaged MK1 and rebuild it for him.
A car was fairly quickly located about an hour’s drive away in a salvage yard
which looked like it would be ideal. An 88 ‘T’ bar with modest mileage and in
pretty good pre-accident condition. Damage was fairly light and was restricted
to the front. Repair would require new bumper, bonnet, front panelwork behind
the bumper and nearside wing. By an amazing coincidence the same yard had
another complete car in the same colour with no front damage. After a bit of
wheeling and dealing the second car was also purchased for parts only. It was
very clearly marked as scrap only and even had the vin numbers on the bulkhead
punched out to make sure it was not relicenced. Later inspection showed it to be
a very crude cut and shut job with dexion angle welded into the front chassis
legs to keep it together! Following a couple of weeks of cutting, hammering and
welding, the front of the car was rebuilt using all undamaged panels from the
donor and it was time to turn my attention to the undamaged rear of the rebuild
car.
We had looked at quite a few MK1 ‘s before purchasing the damaged car and
most seemed to have some rot in the rear wheel arches. Our car proved to be no
exception and some cosmetic work was called for.
Using a rotary wire brush revealed fairly extensive rot in both inner and
outer wheel arch sections so I decided the only solution was fairly drastic
surgery and rebuilding. Fortunately the donor car had much better arches and
would provide good repair sections for the project car.
I understand now that new arch repair sections are available which would have
saved me a bit of effort but nevertheless the repair method remains the same.
Having established how much of the arch needed replacing, I cut an
appropriate, but considerably oversize section from the donor car. An angle
grinder or air saw is ideal for this but remember to wear appropriate eye
protection during cutting.
The inner/outer wing construction detail is shown in sketch ‘A’ and having
removed the donor section the first job is to separate the inner and outer
sections. For this you will need to drill out the spot welds around the wing lip
using a spot weld drill bit. These are obtainable for a couple of pounds from
good tool shops and will allow the drilling out of the first layer of spot weld
without going through the lower layer of metal.
Separation of the two pieces revealed that a basic design feature actually
causes the rot to occur. Sandwiched between the two panels at the time of
manufacture is a strip of foam type material. Obviously this was intended to
seal the spot welded joint but in effect only served to retain moisture between
the two layers.
Having separated the two sections, clean off all metal burrs and foam
remnants and overlay the outer repair panel on the project car to make sure you
have a big enough repair section for the rotted area. Mark the outline of the
repair section with a pencil or scribe on the project car.
Using an angle grinder cut the outer skin only, well within the marked area
to remove all the rusted material from the project car. Either drill out or
grind away the welds on the wing lip to leave as much as possible of the inner
arch intact. Now establish how much of the inner arch requires replacement and
similarly overlay the other section and mark again. Now cut out the rot from the
inner arch. The main thing to remember with this portion of the work is that the
outer wing repair section must be wider than the inner section to provide room
for welding (see sketches). Normally repairs of this type would be done using a
stepped lap or butt joint at the original/repair section connection but in this
case two things make a simpler solution possible. The shape of the inner and
outer sections together with the space left by the removal of the foam seal
allow the inner arch to be simply laid over the original panel and welded to it.
The outer wing metal being of quite a thin section can similarly be overlaid
without a stepped joint. After grinding off surplus weld a little filler
conceals the repair. All welding should be done on a hit and miss basis around
the circumference of the sections to avoid distortion and the lip welds should
be completed using the plug weld method through the holes created when removing
the repair panel.
Once welding is completed, grind off all surplus weld and fill and finish
ready for painting. Following painting, undersealing the repair will be
necessary inside the wheel arch as a totally waterproof repair is almost
impossible to achieve. In addition a liberal dose of waxoil applied to the
double skin panel through the sides of the rear boot space will ensure that the
rust bug does not return.
Final words of warning When repairing the nearside of the car, remember you
are working near the fuel filler cap. Keep the cap tightly closed and the access
door shut at all times. Inside the rear boot remove side trims and air cleaner
and intake ductwork to allow inspection and dousing of any internal paint fires.
Disconnect the battery before earthing the welding equipment to the bodywork.
Always wear goggles and or welding mask.
GEOFF BARRON
ARCHES
I am rebuilding my MK1 and I have kept in touch with your web site. Whilst I was
wandering through a breakers yard about a week ago I came across some plastic
rear arch covers attached to a VW Golf. I measured the rake and took them home
to find that with a bit of adjusting and trimming they are quite a good fit. A
cheaper option for someone that wants a quick solution. Just thought I'd let you
know, regards Mike, Warwickshire
SPRING CLEANING
Now that the worst
of winter is (hopefully) behind us, it really is time to think about doing those
jobs conveniently 'postponed' whilst the weather was inclement. Before members
rush out with the shampoo and polish (-well I'm told its not only 'Darren the
undisputed Polishing King'!), -- its actually more profitable if not as
gratifying to clean off the underside first.
The most important
areas are those rear wheel arch lips - as they are so prone to rusting from the
winters build-up of mud and salt.
Unfortunately,
armed with only a hosepipe I generally end up getting more soaked than the car!
Despite the mess it definitely pays dividends -- but each time I swear blind
that I must really get a pressure washer with an underbody jet to reach into the
arch - has anybody tried one with any success?
ALAN JONES