Restoration Project – Andrew Atwood
STRUCTURAL METAL WORK
Part Four of an ongoing series
At the end of Part Three, I had just sent my stripped chassis and sheet-metal panels for media blasting to remove 50 years of paint, road grime and bad bodywork previously performed on my car. As I was planning a complete restoration, I wanted a clean slate to start with; this is a must when you want a good long-lasting paint job as previous poor body work or hidden rust can work its way to the surface and create a lot of problems later.
Stripping the body removed 10 pounds of Bondo and six layers of paint and undercoating – yes, I counted them all. Unfortunately, it also revealed other serious issues that were previously hidden. I might have noticed symptoms of these problems had I done a proper pre-purchase inspection, but as you may remember from my first article, I made an emotional purchase – never saw them.
My relatively nice straight body came back from the blaster looking like a cross between a sheet of corrugated steel and a pasta colander. Both front fenders and lower rockers looked like Swiss cheese and the left-rear quarter panel and the doors looked like they had all been opened into fence posts. The only reasonably straight panels were the roof and hood. I almost cried.
No matter. I was now committed financially and emotionally and took these as challenges to overcome. Fortunately, I enjoy bodywork as much as I enjoy building engines and had the necessary training and experience to do the job myself. If you reach this stage in your restoration, it may be time to look for a good body shop with experience on Mercedes-Benz cars.
The extent of the problem
Taking stock of my task, I determined that the front fenders, rocker panels, and left-rear quarter panel were too far gone with rust to feasibly repair. They all would have to be replaced.
Replacing a front fender merely requires basic hand tools and patience, but front fenders for this model are NLA (no longer available) from Mercedes-Benz, so I had to source them elsewhere. Through due diligence, I found several sad-looking W111s on craigslist.com for under $600. Even if I only used the fenders off each car and junked the rest, it would be a bargain. As it turned out, one had a good left fender and the other, a good right. What luck! Now I not only had two good fenders, but also a wealth of spare nuts, bolts and other interior bits, not to mention that one of the cars had a sun roof just like my car, which I expected might come in handy later.
Junked cars can be a great source for parts. Rather than searching for that one elusive part, buy the whole car, take what you need and sell the rest. I have done this numerous times and sometimes made a profit after stripping the car of parts I needed.
The rear quarter and lower rockers were another story. I had to take a step back and reassess what I was going to do with the body; I had set budget limits for bodywork and paint. On a unibody automobile, replacement of quarter panels must be performed very carefully. Lower rocker panels are even more critical. Otherwise, there is a big risk in damaging the car beyond repair or, at a minimum, not having the doors line up or even close properly. I've done sheet-metal work in the past and my aviation experience helped me immensely in knowing I could do the work.
But that wasn’t all I was facing. Upon closer inspection of the body, I found another depressing aspect. This car had been in a rear-end accident and repaired very badly. I also noticed that the left-rear quarter and the rear taillight panel were once replaced and welded with oxyacetylene, which would indicate a 1960s or ’70s’ repair job. Whoever did the repairs not only welded the panels crooked, but also welded all the drain holes; thus, the left rear of the car rusted whereas the right side was rust-free and solid.
So now I had to add the lower back panel to my list of needed parts; this was starting to seem very daunting. This is the stage where a lot of restoration projects stall and die, which is why it is so important to have the car you are purchasing, or going to restore, thoroughly inspected before you start.
Again though, because I love sheet-metal work, I was actually looking forward to tackling this job. I made a parts list and called my Mercedes dealer and began the parts search and budgeting. Thankfully, Mercedes still supports the Heckflosse (fintail-bodied cars) and a rear-quarter panel was only $1,300; the taillight panel was available for the low cost of $1,600.
I was a bit shocked with the prices, but when I considered cutting up another car versus using new parts, I decided to order the new parts. I knew they would give me a much better chance of having a straight car as well as make my job less labor-intensive. The lower rockers and their accompanying front panels were a relative bargain at under $500 for both sides, but these I knew were going to be a handful to install.
Working from the bottom up
Where to start first was my next decision: rockers or quarter panel? I had to have the main body and doors straight before starting on the rear-quarter panel, so I started with the lower rockers. I borrowed a pinchweld dolly (this grasps the pinchweld seam along the chassis bottom and keeps it straight and true when structural elements are removed and replaced) to support my car while doing this job. Between this and my hoist, this made the job so much easier as I was not lying on my back to do the work.
To start the task, I first made sure all the door gaps were straight and even. If they were not straight before I started, then they would be very difficult to straighten after the rockers were done. I also left the doors and their latches on while I replaced the rockers to double check my work as I was progressed; if something got out of position, it could be repositioned before being welded into place.
To facilitate the removal of the spot welds along the rocker panels, a spot-weld drill and bits are invaluable. This tool made the job so much less labor-intensive and kept me from drilling through both pieces of steel. If you can’t get one, just buy spot-weld drill bits and be very patient. Mercedes placed spot welds every 25mm on the rockers and most other panels, so I drilled out nearly 300 spot welds on the lower rockers alone – one reason the spot-weld drill is invaluable.
To prevent the body from moving or warping during this process, I welded in several cross-braces in the interior of the car before removing the rockers. This is critical and further guaranteed a straight car when done. With the lower rockers removed, I vacuumed five pounds of mud and rust from the inner rocker panels and thoroughly cleaned the inner rockers before spraying them down with rust converter and then a good zinc chromate primer for the ultimate rust protection.
There are two ways to install replacement rockers with that stock spot-welded look. The first and easiest is to use a two- or three-phase spot welder that will emote that factory look. The problem is that not everyone owns a $3,000 spot welder. The second method – just as professional and attractive – is to use rosette welds. This is the process where a hole is drilled or punched into one piece of the sheet metal and the hole is then filled with welding material, thus attaching both pieces with a spot-weld-style look. Both methods have equal strength and are almost identical in look, though the spot-weld approach is quicker and easier.
Another good tip whenever welding two pieces of sheet metal together to prevent that ugly rust that can form along the join of the panels over time is to use a good quality weld-through primer. This can be purchased from most automotive paint supply stores and is effective in promoting good conductivity if you are using a spot welder.
According to the Eastwood Company, “This unique self-etching primer formula has organic binders that replace conductive heavy metals such as copper and zinc. These organic binders will burn off during the welding process, leaving a corrosion-resistant self-etching primer for paint prep. This product will reduce spatter and distortion caused by excessive heat that occurs during the welding process. Compatible with MIG, TIG and arc welding. The metal-etching primer will enhance adhesion and durability and is compatible with most top coats.”
To attach the rocker panels, I was able to use both welding methods. I first used the rosette method in a few places to attach and hold the rockers in place. Then I could use the three-phase spot welder to do the rest. After I stood back and compared the two, I could not tell the difference.
Quarter panels, lower back panel and wheel wells
With the rockers tacked in place, I now turned my attention to the rear-quarter and rear-light panels. Replacing these panels was labor intensive because the rear quarter included the rear-left inner door jamb and inner fender as well, and the amount of rust in the wheelwell made it difficult to find all the spot welds and some of the inner wheelwell had rusted away with the rear quarter.
Now I was replacing the inner-rear wheelwells. Yippee! So guess what was next? More spot-weld drilling. By then I was seeing spot welds in my sleep – those darn Germans and their thoroughness in welding a car together so that it would never fall apart – unlike American cars and their assumed short lifespans.
As I was removing the rear-quarter and lower-back panels, I could see the extent of damage to the car from previous accidents and was able to correct those before installing new factory Mercedes panels. A previous repair shop had welded the rear assemblies on crooked as well, and this explained why the trunk did not fit correctly and why the rear left area had rusted – water leaked into the trunk from the quarter-inch gap between the trunk and quarter panel.
I first temporarily assembled the rear panels with Clecos, which are awesome little devices used in aircraft assembly to hold panels in place until they can be riveted or welded into place. If Clecos aren’t an option, C-clamps or C-clamp-style vise grips work well.
With my body shell perfectly leveled on the dolly, I proceeded to double- and triple-check my measurements on the rear panels before tack-welding them into place. Realistically, I probably used rosette welds on about 25 percent of the welds needed and the rest were spot-welded with the three-phase welder. Once all the panels were tacked in place, I was rewarded when I bolted the deck lid: The gaps were perfect and it closed perfectly for the first time. With the major bodywork completed and the chassis painted in primer to forestall rust, this was cause for celebration.
Next up: Prepping and painting the body panels.
Captions
On the pinchweld dolly, with outer rockers removed, extent of rust can be seen.
Using original-specification parts assures a perfect fit almost every time.
Seeing the car for the first time after media blasting. All sins shall be revealed.
The inner rockers were in good shape and only needed cleaning and painting.
The factory-spec rocker panels helped me line up all the adjacent panels.
Spot-weld drill and hole-punch/joggler are invaluable tools for this work.
The spot-weld drill saved me hours of arm-wrenching work . . .
. . . and it makes perfectly drilled holes for spot welds.
One tool punches holes and prepares the panel for rosette welds.
The rear frame had some rot in it as well that would need to be repaired.
Since this area won’t be visible, the repair just has to be practical.
Once the undercoating is applied, the repair will be completely invisible.
Progress but more bad news as the chassis comes back from the media blasting.
Media blasting exposed other damage, like swiss-cheese rust in the rear quarter.
With the rear quarter panel removed, the extent of accident damage was exposed.
