Body shop W245 edition

– A tale about rusty body panels and Mona Lisa

I cringe when I see rust on on cars. It clearly shows neglect and non interest on the owner’s part. It could be as simple as lack of washing the car, ignoring stone chips or heavy use resulting in deep scratches. However car use in winter conditions where the use of road salt is common, small openings in the paint can cause large rust areas to appear quite fast and the owner can’t always be to blame. Therefore it’s more important to regularly wash the car in the winter than in the summer time. Due to the impossibility to avoid any rust appearing in these conditions, is the reason I keep the vintage classics parked in the winter time. It is very hard to maintain older cars during winter time and the rust is very pervasive into every area. So why not use a disposable B-Class during winter?

So when I took over the B-class of course it had rust after many years winter use in Norway. Luckily all of it is just surface rust, but if not attended to it can develop into holes already in the next winter. Along with the other issues on the car I needed to get this fixed before using it.

Attraction points for rust due to stone chips from the narrow wheel arches.

The B-Class has a design issue in my opinion since the wheels slightly go too far outside the narrow wheel arches and stone chips really eat away the paint on the edges as well as along the sides of the skirts. This is most apparent on the rear wheels, but also an issue in the front. This happen even with the standard tire widths. So expect the paint to be chipped away by default. The car should have really have installed some mud flaps.

I had to address all four wheel arches of varying degree of rust, as well as the area beneath the side skirts and the underside of the drivers door. There was also beginning to form rust in the drain area for the window wiper mechanism on the passenger side. I think the main cause here is winter use,, but it could have been prevented more by washing it more often to get the salt off.

With paint it’s better to do all areas you want to paint in one go since the process of masking and drying of multiple coatings take forever to prepare and do. The painting in itself is the fast part of it. Then you have the surface preparation such as rust removal and making sure it’s completely clean. There could be additional steps of applying filler and sanding to make it even nicer. With this car I totally neglected filler and sanding since achieving the Mona Lisa with this cheap car is not worth it. Remember the longer time you use on a paint job the better the result. I tried to get a balance between visual satisfaction and function. Protect the car from rust while looking nice from 1-2 meters away.

Starting out. There is a small area of rust on the edge of the door as well. And multiple bubbles on the wheel arch needs to be attended. Rust continues on under the side skirt. Need to remove side skirt to get access.
Rust is sanded away with a narrow belt grinder. Super useful tool. The black is a rust converter paint which is clear in colour but turns black in contact with rust and forms a hard coating. This can be used as a primer, but I use a thick primer anyway over it.
Masking and priming paint. After priming the masking have to be removed. To avoid edges in the paint the edge from priming should be sanded down. If not Mona Lisa, you can skip it.
Before applying the metallic paint. Move the masking out and bend the masking paper without sharp edges to feather the new paint against the old. The result will be 100 times better than sharp edges, since the new paint will never have the exact colour of the old paint.
Painted with metallic and clear coat. I used 3 layers of metallic and 3-4 layers of clear. Not perfect but much better than rust. I’m very happy with the results!

Now let’s hope this lasts through the winter. I’m pretty certain that I will have to tend to new stone chip spots in the spring, but that’s the life when they put sand and gravel on the icy covered roads to grind away my paint. Then pour salt in the wounds so the chipped paint can start top rust. Thank you so much, sincerely! Looking forward to the summer already.

So about that Mona Lisa. Close enough huh?!?!?

Funny mona lisa

Robs Out!

How to weld the front fender on w123

The front fender corners on w123 are usually the first thing to rust on these cars due to the factory seam acts as an rust attractor where water will get in eventually. The easiest way to fix this problem is to simply change out the front fenders. Some years ago they were still cheap, but prices are now rising dramatically in some areas. Also replacing the fenders has some issues as well. #1: They might not fit exactly and you will have to do minor body work anyway. #2: The whole part has to be resprayed in matching colour of the car, this can be quite expensive and the colour might be hard to match exactly.

w123 front fender seam
w123 front fender seam. Common rust attractor.

The second option which is cheaper, but more labour intensive is to fix the old fender yourself by welding. This will keep the originality of the car more if you care about these things. As a bonus you will get rid of that seam permanently too, however this will leave a small sign that it has been repaired. I personally think this seam is an ugly feature of the car and that Mercedes really skipped on production costs when making this panel. I have fixed in total of four front fenders for two different cars with this method and have been successful.


As a condition you need to have a decent skill in welding, this panel is quite difficult to weld for the untrained due to the thin body panel and also the curvature in the corner. It is quite easy to burn through and also forming the metal piece of still can be tedious. However if you are as stubborn like me, then don’t be afraid of this task, use your time and go carefully and you will be successful. (I am no master in welding)

Other stuff you need:

  • Steel 0.8mm
  • Welding tool and accessories (TiG is more suited for this, but a high quality MiG is also fine)
  • Paint of your choosing

It can be done with either the front fender off the car or just leave it on, it all really depends on haw bad the rust is. If you are taking the fender off then you have to be really careful of not scratching the paint which is easier said than done. If you can leave it on the car then it is preferred.

Start by removing the front bumper, it is only secured by two big bolts in the front then two small one at the corners.

Locate the rust, start picking out the flakes and the damaged paint to located the where the good metal is. Then start cutting with the power grinder. Cut at least 1-2cm from the rusted metal to ensure only healthy steel is left.

rust removed from fender
Rust removed from fender

As you can see the hole is much larger than the apparent rust area, everything has to go. Now the hole is defined, then take some sheets of paper, thick paper is better, then use a marker to outline the shape you will need to obtain in order to cut the metal.

Once you have cut out the sheet of metal, the shaping starts, also you will need to fine cut it. so it fits exactly over the whole. This part is where you should use most of your time to get it right, since a right fitting is crucial to get a good weld seam. On this section I used in total 3 separate pieces of steel. One for the big curve, one for the top area under the bumper, then one small one for the bumper bolt hole.

welded front fender
Holes welded

After it is welded you should start polishing the metal to the bone to get id of deposits, then the seam needs to be grind down, use a floppy grinding disk that will follow the contours of the surface more. It is important to not grind too much so there will be holes, remember the metal is quite thin! Any last details have to be smoothed down with body filler. Remember a good weld will minimize the amount of after work with filler, so you should try to make this first step as good as possible.

front fender weld seam grind down
Weld seam grind down

Then the rust protecting base coat have to applied before the body filler. Many use body filler before the base coat, this is not recommended since body filler can attract moisture.

First base coating
First base coating

Start applying body filler to smooth out the last irregularities. When working with car cosmetics the rule is usually greater result with more time spent, but time is precious and only use the time necessary to get the result you want. The area which is going behind the bumper doesn’t have to be perfect since no one sees it. Also remember the back side where all the dirt and stone chips are hitting. This should have a thick layer of paint of any colour and some body protective coating that can withstand stone chips.

body filler
Body filler

Use the sand paper to smooth the filler down and feel with your hand that you get the result you are looking for, you might end up doing this two or three times and a fast drying filler makes things quicker.

Second and 3rd base coat over after filler
Second and 3rd base coat over after filler

Apply the second and third base coat after. Then let it dry completely before you start spraying with the nice top paint. Be sure to use many thin layers instead of one thick one which will start running, then all your work is ruined. The hardest with paining is definitely making an even coating without it starting to run.

Base coat finished
Base coat finished

I couldn’t paint the top coat the same week, so I had to use the car with the paint like this for while. But this is anyway how it looks if you don’t paint your car in the same colour.

So then when possible paint the top colour to make a perfect finish.

front fender painted and finished
Front fender painted and finished

I was quite pleased with the result, no seam and smooth finish, basically no trace of former rust.


How to service your Sunroof (manual) on W123

Sun is shining and the car has been standing all day in the heat, you open the door and when the extreme desert heat punches you in the face like a big angry and scorching red Finnish man of a beast who just has been sitting 30 minutes in the sauna. You might starting to have seconds thoughts about driving when your car is nearing 80°C inside. Anyway you man up and get in the car because you actually have to go some places and do stuff. What other thing could be more annoying than a stuck sunroof so you can cool down (I’m assuming your air conditioner is not working)?

Maintenance of the sunroof mechanism is to prevent such scenarios and also keep the sunroof motor from getting destroyed, of if you have a manual sunroof, then the handle can actually break off. Then you would be sitting there and sweating your ass off. Imagine the opposite case, where you can’t close it and it rains!

There is one way to prevent this situations for happening, clean and grease those sunroof tracks!

I will only cover the manual sunroof here, the only difference from the electric one is a cable which you have to extract, and that is quite messy.


On this particular demonstration car, a 300TD wagon with a manual sunroof, it was a pain to open and it ended up never being used. So I finally got myself to unbolt the sunroof and properly clean those tracks and glide feet of the roof. Then lubricating it with some special Mercedes sunroof grease before putting it all together. The process is quite easy, however you have to be careful not to damage the inner sunroof lining or chip the paintwork when you take it out.

So you need special purpose sunroof grease from Mercedes, I really mean this, it will last 15 years and can withstand the rain. I got mine from where they sell kits to do this job, you can also go to a dealer which is probably more expensive.

No special tools are needed.


Unscrew those two side plates when your sunroof is open, 8 philips screws in total. Let the flat head screw be there, it’s just for adjusting.

sunroof side plates w123
Side plates

Unscrew the decorative plate for the handle, keep in mind that it’s made of plastic so it can break easily. Especially since it’s old and brittle. You can not remove the cover so you have to push it carefully through the head lining, since the head lining is coming off in the next step.

plastic handle cover sunroof
Plastic handle cover

The head lining is held up by some metal clips in the metal of the sunroof, just grab the front end of the lining and pull down until the metal clips are free, taking care the plastic cover comes through the hole at the same time.

headlining sunroof
Pull down hard on the edge of the headlining sunroof

Remove the head liner by pulling it out while the sunroof is open.

Then unbolt two 8mm bolts as seen on the picture under, same on both sides, these hold down a plate which holds a crossbar, keeping the sunroof attached to its’ rail.

unbolting sunroof
Unbolt the sunroof crossbar

The Sunroof can now be taken out, take great care of not scratching the paint of the sunroof or the body of the car while taking it out. Get help from someone if you find it difficult although it’s not very heavy.

sunroof taken out
Sunroof is taken out, now it’s like having a cabriolet…heh

Start by removing the old grease on the plastic glider feet pads on the sunroof and the guiding rail on the car. If the plastic feet are broken, then you might have a hard time getting replacements, this is why preventative maintenance is the best maintenance. Sure you will be thinking I’m a smartass…

glider feet sunroof
Clean and lubricate the glider feets

Grease all 4 white plastic feet, don’t grease the black pads made of cloth.

glider feet sunroof
More feets..


Again it is important that you grease the tracks and rails with Mercedes  special sun roof grease, this is to do with the engineered properties the grease has to resist water from the drains and still provide lubrication without flushing away, and it’s very long lasting. I think this is the first time the sunroof has been greased on this particular car since it was new, 28 years ago.

sunroof rails
Clean the sunroof rails

Clean the rails and grease the other side of the the top edge that the screw holes are. Note the position of the plastic feet and the cloth pads. Only grease the rail where the plastic feet are touching and not the cloth, or you will have a sticky sunroof.

guide arms sunroof
Grease the pivot arms

Once cleaned and greased up in the right places, you could assemble the sunroof reverse of removal.

Feel how easy the sunroof slides compared to before, it should slide effortlessly back and forth.