Mercedes-Benz Ponton 220S Sedan
Restoration Story / Part 4

Contents

Engine Compartment

Exhaust Resonator

The "muffler" on the exhaust manifold was dented and had some holes at the bottom end, though the pipes were sound. I checked at a local muffler shop for something that could be retrofitted, but it would be a bunch of trouble because of the two pipes coming in at one end. Though it was probably possible to weld something up, I decided to see if mine was repairable. Using a tiny cut-off wheel, I removed the outer metal cover by cutting along the base of the pinch welds. I carefully removed the asbestos insulation pieces. I set these aside where the fibers would not be disturbed.

Using an air cut-off wheel, I cut out the rusted and dented part of the resonator and sandblasted the inside and outside. After sandblasting, I could even read the original supplier's name and part number. It is interesting that it is divided into two halves internally.

The top half is simply an open chamber where the two pipes come in.

From body repair sheet metal, I fabricated a new replacement piece and took it to a car restorer who welded it in. I painted the whole thing with the high temperature silver paint from POR-15. This paint "cures" at 350 degrees, so I cooked it in the oven. Don't do this in your food oven unless you live alone and don't mind the very strong chemical smell that will stink up the whole house. Though this paint will rub off and marks easily before it is cured, it is very tough after curing.

I got some thin galvanized sheet metal and fabricated a new outer cover piece. It was tricky to form the stepped ends. I made a kind of form from metal strips and a hose clamp around a piece of 6" PVC pipe, then crimped the ends down over the "form" with pliers. I cleaned the asbestos insulation (very carefully, outside, wearing a mask) and painted it with the high temperature paint to prevent further fiber disintegration. I had the same welder tack the cover together and to the resonator.

I used a piece of coat hanger wire to measure the angles and length needed for a piece to connect the resonator to the remains of my exhaust system. I took it to a local muffler shop where they graciously made a connecting piece for free (though it took 3 tries and two trips) and I promised to drive the car to them later for a whole replacement system.

Heater Duct Flaps

Steering Damper

I have heard a rumor that is it possible to use a later damper (for a sixties MB that cost about $25) that has the "eye" end at both ends. A special bolt adapts the eye end to the hole in the pitman arm.

Brakes

On each backing plate is a small aluminum housing containing a pulley where the parking brake cable goes in, and cleaning off the 40 year's worth of petrified dirt and grease reveals a nice aluminum housing. I had to re-set the cable adjustment at the equalizing lever (right above the drive shaft at the differential) to get enough slack in the parking cable to allow me to connect the lever under the hood (I found out later why the cable seemed so short - see the section below on first drive). That was messy also, but it was an opportunity to remove and clean these parts to like-new condition.

If you only need the rubber seals and don't need the hard parts for your wheel cylinders, you can get replacement rubber seals from any parts store that carries brake kits for American cars. Mercedes' suppliers used inch sizes on the bores and seals, like most (all?) other manufacturers. Just look at the size written on the seal and ask the parts guy to look up something that uses that size (15/16"). My replacement seals were for a mid-sixties Chevy and cost about $3.00 for each corner. Note on the seals: there are two basic designs: with and without an "expander" piece to help expand the seal against the bore. If the new seals don't come with expanders (as did the originals), don't use the old expanders and instead use the custom springs that come with the new seals.

I replaced the rear flex hoses without any grief. The fronts also came off easily, but they had been removed around 1980.

I bled the brakes with my vacuum pump system, but there was still some air somewhere. Got my wife to help do it conventionally and the air was in the fronts.

Rear Axle Bearings and Seals

Getting the inner seal installed in the axle tube was also a bit of trouble without the special tool. If you replace this, have someone with a lathe make you a proper tool to drive it into place - it will be worth it. Use a thin coat of silicone sealant around the outside edges.

For installing the outer seal into the retaining plate, I made a "press" with some small plates of metal and used my vice to press the seal into place. This way it gets pressed in squarely and doesn't damage the seal. I used the old seal to press it the final few millimeters.

Then, while installing the axle, I discovered that I installed one of the bearing retaining plates (and the seal in it) backwards and had to do one axle all over again! Well, it sure LOOKS like it should go the other way. :-(

Engine Start

The gas tank is not yet installed, so I used an oil bottle for gas and a line to the fuel pump. I held a rag around the top of the bottle and pressurized the bottle with an air nozzle to force gas through the pump and into the carbs. This primes the pump and saves the starter.

I statically set the timing and checked all the wiring. New battery, hooked it up, looked for sparking on connection; OK. Tried the starter for a second; OK. Checked for gas at the carbs; OK. Checked for accelerator pumps squirting; NOT OK. So removed the accelerator pump diaphragms and cleaned; about two hours of fiddling around and cleaning. Reinstalled; OK. Tried the starter and instant vroom! Nice! No strange noises, no leaks; OK. After a minute or so it even idled on its own. Ran it until it fully warmed up, then shut it off.

The next running was a few weeks later when I drove it up and down the street a few times. No front fenders yet, so no lights; no gas tank so can't go far anyway! Brakes work OK, stops straight. Some noises from drive line when coasting; later investigation on my lift showed the parking brake cable was wrapped once around the drive shaft, so I had to take the lever off to unwrap it from the front half of the shaft. If that's all I did wrong, I consider that good!

Rust Repair

Jack also sent me new door hinge screws and a new screw plate. I had to drill out several of the rusted screws.

I added an "x" brace to the radiator frame. I had long noticed that the whole front end would shake side to side on severe bumps, and I noticed that Kevin Clemens added the same kind of brace to his "Around-the-World" rallye car. I got some screen door adjusting rods, cut them and beveled the ends, and made a small depression where they will be tack welded to the lower front cross member in front of the radiator.

The spot welds to the right side of the inner fender are partly rusted and partly just broken, so those will be re-tacked by my welder.

Extra Sound Insulation

Foam Sound Deadening

Kick Panels

Suspension Rebound Stops

Speedometer

Once in the past, my speedometer filled with grease and indicated many times higher than it should. The grease was pumped up the drive cable (like an Archimedes screw) and filled the drive mechanism. The drag on the grease is like a viscous drive coupling (normally, there is air between the spinning magnetic disk and the driven cylinder) and makes the speedometer read very high - it pegs out when going only about 20 to 30 mph, depending on temperature. It had happened again just before I disassembled the car. The inside of the speedometer is a fine piece of craftsmanship and assembled like a fine instrument.

Speedometer pieces after disassembly and before cleaning. Disk (lower left) shows grease that got inside, half wiped off. Cylinder for disk above, with grease inside. Die-cast drive piece to right. Cable is for odometer reset. Small gears are for odometer drive.

Front of speedometer case

The indicator needle is moved by a VERY thin wire (about the thickness of a human hair) that is wrapped around a spiral-grooved drum that is driven by the spinning input disk. Pulleys at each end guide the wire around the ends of the scale where the guide rods for the indicator needle are attached.

Back of speedometer mechanism, gauge mask, gas gauge, and lamps

To Disassemble the Speedometer

1. Remove the speedometer unit from the dash. Despite what the manual says, you don't need to totally remove the temperature gauge capillary tube from the car; you only need enough slack to be able to remove the 3 screws on the back that attach the temperature gauge (though it's a little difficult working backwards and blind while trying not to scratch the dash or steering column).
2. Carefully pry the chrome surround off the case, starting at one end. It doesn't need to be bent significantly to remove it, but having three hands helps.
3. Remove the glass. It's held with sticky tape so it may take a small suction cup to get a grip on it. Remove the mask for the scales.
4. Remove the four screws in the back that attach the speedometer drive mechanism and remove the speedometer and mechanism with scale.
5. Remove the screws in the back that hold the drive mechanism on. Watch for washers and spacers, especially the very tiny washer on the pin that centers the driven cylinder on the spiral drum.
6. There is a thin metal washer and a thin rubber washer sandwiched behind the die-cast piece (that holds the shaft of the spinning disk, where the speedometer cable attaches) and the cylinder that houses the spinning disk. I think the rubber seal is supposed to keep any oil or grease from getting past, and there is a groove on the back of the cast piece that will let the fluid out to the side. To repair the worn rubber washer, I put some silicone sealant on it when I reassembled.
7. Behind the odometer scale on the left side, under one of the screws, is a piece of metal that acts as a stop for the return spring. When reassembling, adjust this so the needle rests exactly on zero.
8. Use a soft camera lens cleaning brush to clean the scales and other parts.
9. One of the pulleys is mounted on a separate piece that allows adjustment of the tension on the wire. There is a tiny tension spring at one end of the wire where it attaches to the indicator needle. This spring was completely slack, so I loosened the screw and moved the pulley outwards a little to take up the slack.
10. The speedometer is calibrated via an adjustment nut (located behind the scale and below the spiral drum) that adjusts the tension on the main spring that returns the needle to zero. If you have a way to accurately spin the input shaft so the odometer increments one mile every 60 seconds, you can adjust the tension spring so the needle reads 60 mph (1 mile/minute). (I did not try this and I suggest you use a speedo repair shop.) You cannot "calibrate" the odometer because it is direct drive at a fixed ratio. If you need to calibrate your odometer and speedometer to your car because you have tires of a different diameter than stock, you need a small gearbox that connects between the transmission and the speedo cable to change the overall ratio. These used to be available in various ratios.
11. My sandblasting of the engine compartment managed to get some sand inside the speedometer case (I'm sure I'll be finding sand in strange places for years to come?). There are holes in the tiny rivets along the bottom that hold the clips for the wiring, and gaps around the holders for the indicator lights. I these filled these openings with little dabs of caulking.

Back of speedometer housing and instrument, before reassembly. Adjustable pulley end for tensioning the wire is visible on left end of speedometer mechanism

Cleaning the Fuel Lines

Fender Straightening