Mercedes Benz 190SL

The boot floor was in excellent condition considering that most 190SL's I have viewed have water penetration past the rubber weather strip. Eventually rusting away the channel where the weather strip bonds to with rust settling in the lower parts of the wheel wells and boot floor. Preparing the floor to accept its first coats of paint was easy. What was not easy was treating the inner wings up to the 'B' posts as my rear wings had not been removed. The entire floor and rear wings were acid washed with POR15 Metal Ready in a plastic spray bottle. This allowed the acid to be sprayed deep into the inner wings. Several costs were applied including to all joints on the boot floor with a hard brush and 3m Scotch Brite pad until all signs of surface rust were removed. The acid was continually sprayed with water from a plastic spray bottle to keep the acid from drying and to reactivate it. After soaking in acid for 20 minutes the floor was thoroughly washed down with warm water and immediately dried before any rust formed.
Notice in the photo of the boot floor the original factory grey/tan primer PPG's DAR 4065 "Sandalwood." In fact this colour can be found on the seat base frames, behind the dash and probably under the colour coated body. The factory did not colour code the floors and had they been aware of rust would have probably provided greater protection to the undercarriage of these cars. In fact the frame box sections were never painted nor were coated with rust preventative material. That is why these cars rust from the inside out.

The dry floor was then sanded with 3m Scotch brite pad and cleaned with panel wipe and degreaser. I used a Devilbiss GTI gravity feed gun with a 1.4mm tip to spray the floors with three coats of PPG DP40 epoxy primer. This should provide sufficient coats to seal the metal over which was sprayed 3M smooth anti chip coating, Grey part number: 08886. I like this product as it is smooth and overpaintable and sharing the same, robust anti-chip benefits of the textured product, 3M™ Smooth Coating dries rapidly to an excellent finish. Applied using the pressure adjustable air-fed 3M Pressure Pot Stonechip Applicator gun gives the best results.

The joints were seam sealed with Wurth Polyurethane adhesive and sealing compound. Product 0890 100 2 Grey using a hand application gun. A further coat of PPG DP40 epoxy primer will follow three coats of PPG Semi-Gloss black DB167 or RAL7167 (DB164 or DB167 Tiefdunkelgrau Matt) in the inner boot floor and the undercarriage side will be painted PPG's DAR 4065 "Sandalwood".

Incidentally any one planning on replacing the rear wings and or the rear panel should pay particular attention to how these parts were joined at the Mercedes-Benz factory to the boot floor. The outer sides of the boot floor had a felt strip between the lip of this panel and the rear wings. The felt should be removed and replaced with a modern sealer after de-rusting as it acts as a wick soaking up water and rusting these two sections. Ensure that the outer floor is not welded to the rear wings at this section otherwise the rear wings will distort with stress marks at the meeting points. The lip on the rear of the boot floor should be spot welded to the rear panel. The factory's welding equipment and workers were remarkable as there was very little distortion or dimples on the outside of the rear panel. Once spot welded any dimples should be finished with lead even though this area will be behind the rear bumper centre section. All joints should be sealed after epoxy priming.

Posted by webmaster at 10:18 PM | Permalink

With the welding, grinding and sanding behind me it was time to prepare the floor to accept its first coats of paint. The entire floor was acid washed with POR15 Metal Ready. Several costs were applied including to all joints with a hard brush and 3m Scotch Brite pad until all signs of surface rust were removed. The acid was continually sprayed with water from a plastic spray bottle to keep the acid from drying and to reactivate it. After soaking in acid for 20 minutes the floor was thoroughly washed down with warm water and immediately dried before any rust formed.
The dry floor was then sanded with 3m Scotch Brite pad and cleaned with panel wipe and degreaser. I used a Devilbiss GTI gravity feed gun with a 1.4mm tip to spray the floors with three coats of PPG DP40 epoxy primer. This should provide sufficient coats to seal the metal over which was sprayed 3M smooth anti chip coating, Grey part number: 08886. I like this product as it is smooth and overpaintable and sharing the same, robust anti-chip benefits of the textured product, 3M™ Smooth Coating dries rapidly to an excellent finish. Applied using the pressure adjustable air-fed 3M Pressure Pot Stonechip Applicator gun gives the best results.

The floor pan joints were seam sealed with Wurth Polyurethane adhesive and sealing compound. Product 0890 100 2 Grey using a hand application gun. A further coat of PPG DP40 epoxy primer will follow three coats of PPG Semi-Gloss black DB167 or RAL7167 (DB164 or DB167 Tiefdunkelgrau Matt).

The paint codes quoted from Mercedes-Benz documentation supplied by the Classic Centre were:

DB-Nr. 167 oder RAL 7167 (tiefdunkelgrau - low dark gray)
MB teilenr. A 00 986 67 33/7167

The 190SL Group technical manual quotes this as A000 986 67 33/7164.

Looking at the Glasurit Color-online both these codes MB7167 and MB7164 come up as Tiefdunkelgrau Matt.

I had my local paint supplier mix up the DB167 RAL7167 and it looks very close to the original colour from the flap below the fuse box cover and is not Matt but semi-gloss.

Wurth list in their catalogue the MB167 as an aerosol 400ml can code number 0893 349 167.

Posted by webmaster at 09:51 PM | Permalink

I have not had a chance to work on the car for a few months. Now that time permits I have finished welding and grinding the plug weld spots of the left hand rear floor section. As it is hard work welding and grinding on your back, I looked at purchasing a Rotisserie, but could not justify the cost. Instead I shall proceed with the project in it's current manner.

I additionally decided to replace the left hand lower firewall as the right hand side came out nicely and since I do not have a streatcher and shirinker to hand, as the lower edge that joins to the front floor pan is curved. The rear floor sections are easier to weld in as there is more space. I have decided to remove the engine and turn the body on its side to aid welding, grinding and painting. On removing the engine by lowering the sub frame with the engine and gear box, the body could not be raised high enough to wheel out the complete unit. Instead the gear box will need to be removed from under the car. The engine can then be removed using a hoist from top, which should give me more room to wheel out the sub frame on its tyres. That job I have postponed until I am able to rally up a few more helping hands.

The factory spot welded the floor pans on to the main chassis sections. This was done before the outer body panels were welded on. As I do not have a single sided spot welder, I made good by punching holes on the edge of the floor pans where the spot welds would be and plug welded the holes. I additionally seam welded the inner side for added protection. The factory did seam weld at the rear portion where the floor curves upwards. I was concerned if my welds would hold up. Tests on a few weld spots proved my welds should hold up.

I plan on cleaning the surface rust by sanding and acid wash when all the welding is done.

Plan for next week is to have the right rear floor pan welded in. It does require a bit of cutting to make it fit. These cars were hand made and each panel was cut to shape before fit, so you can not just buy new panels from the factory and expect them to fit. The worst case I have come across was rear quarter panel, the edge that meets the boot lid on the left hand panel are a quarter of an inch too short. Mercedes Benz are aware of this mis-fit but suggest that the panel should be cut and a piece welded. One would not expect that kind of adjustment for panel fit.

This was the longest next week. More cutting and grinding was needed than I had thought to make this panel fit well. Once the rear sides were cut the panel welded nicely. This photo shows the welded panel which still requires finishing with the grinder. Progress this week was made on getting the front right hand floor pan ready for welding. This should be welded in by the end of this week. Luckly this panel does not need the cutting and grinding that the rear panels required.

All box sections like the rears were sealed with Wurth cavity wax after painting. This should safe guard against future rust.

Commenced working on front right floor pan. Easier to weld than the rears as no curves and bracekts in the way. The lower firewall welded excellently and fit was perfect. As this side has come out well I have decided to change the lefthand lower fire wall too, before welding in the last floor pan. I can see the end to the welding, as after the lefthand firewall, left fron floor just the seat support panels left.

Will need to decide soon the best way to turn the body over so that I can start the preparation work to paint the underneath.

Welded the last floor pan today. Looks good but hard work. Lots of grinding next under the floor pans. This should achieve an original finish like the factory spot weld. These were the most difficult parts to restore, as the floor pans need to be fit from underneath.

I would advise anyone doing the same job to invest in a rotisserie. This is one job that I would not like to do again. The cost of Chassis Tilter at £899 appears a lot to throw into one restoration but it would have saved a considerable amount of time.

The next project is the seat support boxes. Trial fit indicated that lost of adjustment, grinding and rebending will be need to make these fit. These were sourced from Jacksons Mercedes Benz main agent and I am suprised by the poor fit quality. It appears that these are not genuine parts but reproductions sourced from out side the dealership network.

Time for decisions on turning the car over so that I can start preparation of the underneath. I will let you know how I get on next time.

Above photos show trial fit of the seat support brackets. One lower seat pan was bent and needed straightening. The seat pan did not glide on its runners smoothly without much fabrication and adjustments to the seat support brackets.

Posted by webmaster at 03:41 PM | Permalink

The right lower firewall had previously been repaired without much success. The fabricated panel had been lap welded, which would in the future cause a water trap and further rust problems. In addition to this the old panels were not de-rusted.

The only way forward was to cut this out to sound metal and butt weld a replacement panel.An air cut off tool was used to cut out the rusted panel. A paper template was made and transfered to the new reproduction panel. The usual tip of measure twice and cut once was adopted in order to ensure correct fitment first time. This was then given a slight tappered edge to assist strenghting the weld and coated with a weld through primer.

Posted by webmaster at 12:33 AM | Permalink

Apart from the floor pans and lower fire walls the inner chassis rigger required attention. The first photo shows the state of this chassis member before treatment. Treatment used was to cut out rusty metal to sound metal, sandblast, acid wash, epoxy primer, and final coat of Wurth cavity wax Wurth. Fabricated panel was then butt welded and ground flat.

Posted by webmaster at 12:09 AM | Permalink

The original floor pans looked solid but on proceeding to strip them on both sides this revealed a number of small holes in various places. I spent many hours on my back scrapping off the old paint, which just peeled off. I used a blunt chiesel and 3m stripping disc's mounted on a drill to quickly proceed to bare metal.

I decided to replace the complete interior floor pans with new replacement panels. The seat support boxes again looked solid but on cutting these out revealed that these were rusting from inside out and would have eventually collapsed. Mercedes-Benz never painted primer or sprayed anything else on the insides of the frame and box sections of the 190SL, which means that the insides of all box sections are prone to rust. The entire frame and floors should be inspected properly. The best method is to use a pick hammer and tap each part being inspected as described in The International 190SL Group's book Mercedes-Benz 1955-1963 Restoration and Ownership.

The floor pans and seat supports were cut out by drilling out the original spot welds with a spot weld cutter. The resulting spot welds were ground down. With all mating surfaces smooth and further welding to damaged chassis lips the chassis was sandblasted and then acid washed. All inner box cross sections were primed with PPG DP40 epoxy primer and sprayed with Wurth cavity wax.



The floor panels come in four sections, left/right and front/rear. Although these came from Mercedes Benz the quality was much to be desired. The rear left panel required very little cutting and adjustment to make a perfect fit, but the right rear was a few cm's too long all around and was not pressed in the centre of the panel. This required many hours of measurement, cutting, grinding and trial fitment before the panel was ready for welding. I have heard of left rear quarter wings being out of alignment too. All I can think of is that these parts are reporduction and not pressed from the original tooling.

This photo shows a trial fitment of the floor pans, which were aligned and marked up before cutting. Notice the original blue DB334 colour of the car evidenced after removing the sills in the lower left of the photo. The car has had its colour changed to black DB040.

The floor pans on a 190SL are originally lifted up onto the chassis from underneath and spot welded to the lip of the chassis members. Spot welder arms would not reach as the outer panels were fittedby the factory after spot welding the floor pans. I wanted to keep the look of the floor pans as original as possible. The only way to achieve this was to plug weld. A punch/joggler was used to punch holes every inch or so. The resulting plug was welded from the centre in short busts to the outer edge of the hole. This inverted welding position took sometime getting used and to set the mig welder and wire speed correct as I was welding in the inverted position. The floor pans and the part I was plug welding onto were 2mm thick so I had no problem with burning through. To stop the molten weld bead dropping out onto you, you need to strike the centre of the plug with the wire hot and fast. The resulting weld bead was then ground flat. As an additional security I stich welded the panels together on the inside of the car. The factory stich welded in serveral places inside the car too.

Posted by webmaster at 10:51 PM | Permalink