Further Down the Rabbit Hole

October, 1955 issue

I am deep into mechanical work on the car now and I haven't been taking many photos. This is for three reasons. 1. I am too busy working on it to remember to take pictures of the process, 2. My hands are too greasy to want to touch the camera, and 3. Any photos would be of engine and brake parts and probably not all that interesting to look at. So, because a blog post is always more entertaining if there are pictures in it, I am including vintage 190SL photos that I found on the web.

You never know how much trouble you are in for when resurrecting an old car. I got a new brake master cylinder but it is not exactly the same as the old one. The exact one is not available, apparently. Here is the possibly boring story.

1955 was the first year of 190SL production. That first year did not have a brake booster so the master cylinder was designed to work without one. In 1956, the year of our car, they started using brake boosters and a different master cylinder. For two years, 1956 and 1957, the brake light switch, which operates on brake fluid pressure, was attached to the end of the master cylinder. In 1958 they moved the brake light switch to the brake booster. The hole in the master cylinder where the switch used to go is now sealed off. The only master cylinders available now are designed for 1958 and newer cars. So we have to find somewhere else to put the switch.

To do this so that it matches the way Mercedes designed it requires the purchase of more parts. There is a "Y" fitting that costs $45. But this fitting is pretty thick so I would have to buy the hollow bolt that mounts it ($28). Then I would have to get a different switch because the mounting holes are different sizes. I can't even find that part.

What I think we will do is just put a generic pressure switch in the brake line that goes between the master cylinder and the brake booster. This will work fine even though it is not the way the car was originally put together.

A rendering from the 1957 190SL dealer catalog

The carburetors are another rabbit hole I am falling down and don't know how far it will go. This car has its original Solex carbs. I am SO glad I have these! To buy new ones would cost an unbelievably huge amount of money. Fortunately I don't have to buy new ones. The ones I have are leaking from the bottom though. Perhaps it's just a couple of gaskets?

I checked a diagram of the carb. It is not a couple of gaskets. What is leaking are the accelerator pump diaphragms. Maybe the cover plates just need to be tightened. I will try that next time I work on the car. If  the diaphragms are bad they will have to be replaced. A pair of new ones costs $320. Ouch!

I am missing all except one of the gaskets for where the air intake plenum (190SL folks call it an air log) attaches to the carburetors. They are paper gaskets and aren't that expensive but even cheaper is to make them myself using gasket material. That's what I will do. I will use the one that I have as a template and cut three more and it should be good.

On the assembly line in February, 1958

There are two carburetors linked together on this engine. The fuel lines are a bit complex. The one that connects to the rear carb needs to be replaced. Unfortunately I cannot just buy that piece. I would have to buy the whole assembly which is $350. I think we will try to make just the piece we need and not replace the whole assembly.

When looking closer at the carbs we noticed paper stuck in two of the ball and cup linkage fittings. This must have been because they were popping out due to wear in the fittings. I am sure the paper won't last long so I will have to order some new ones. Fortunately these are not expensive.

We pressure-washed the underside of the car this afternoon. There was a lot of oil, grease and dirt under there. We got it mostly clean and then put it up on the lift to inspect it all. There are about 30 grease fittings!  Every moving part of the front and rear suspension had one or two fittings. We greased them all so they should now be good.

Not everything is bad news on the way down the rabbit hole. We discovered that the center link tie rod was loose and, fortunately, it was just a big nut that needed tightening. A super easy fix. We discovered that the differential is not leaking gear oil. What we thought was gear oil was just old grease that had broken down. We also inspected a rubber boot that often goes bad on the rear swing axle. It turns out that it was replaced with a new one back when the car was being worked on in the early 80's. It is in perfect shape.

This truck is awesome!

The drain plug on the oil pan is all rounded off so I am going to order a new one. Lucky for me it is inexpensive and not hard to get. The valve cover gasket also needs replacing. It's not super cheap but it's not expensive either. Only about $30.

I have been working on this car for about a year and a half now in my spare time. It is starting to feel sometimes like it will never get done. There is so much left to do! But every time I work on it some small bit of progress is made so I suppose, at some point, I will actually get in the car, start it up, and drive around. Between now and then, though, I am sure there will be plenty more discoveries both pleasant and unpleasant.

Will the accelerator pump diaphragms need replacing? Will we get a brake light switch to fit the way we want it to? Will I be able to successfully get the brake booster back together? Will the brakes even work when the whole system is fully assembled? Stay tuned!

This pic is from the 1957 dealer catalog

The Big Push

Last Tuesday I loaded the car on my trailer for a trip to a friend's auto repair shop. He has lifts and a huge selection of tools as well as people who are used to working on cars all the time, unlike me who is a dabbler. The plan was to install all the new brake parts, fix or repair other brake parts, and get a look at the underside of the car to see what else it needs.

I had a helper, but really I was his helper. Nick has been working on cars his whole adult life and has the skill and confidence that I don't have. I always get frustrated when something doesn't come apart easily and I often end up breaking things. He knew just how to get stuck things unstuck.

We got it up on the lift and started working. The first project was to remove the brake master cylinder which is in a spot that would be extremely difficult to get to if the car was on the ground or even up on jack stands. Up on the lift, it was much easier but still a challenge. Nick worked on this while I took the wheels and hubs off and got all the brake parts for the wheels ready to install.

We spent all day working on the car and got the master cylinder removed, the front brakes done and one of the rear brakes. I repacked the front wheel bearings, too. The master cylinder was pitted, as I suspected, so I ordered a new one. It should be here tomorrow. I thought about sending the old one to be re-sleeved but that would take a couple of weeks. The new one will get here sooner.

Nick discovered that the center link tie rod needed to be replaced. Fortunately I have one that was bought for the car 30 years ago and never put on. Also the oil pan and differential leak so we will try to do something about that while the car is there.

The first wheel cylinder gets installed

The next day I couldn't go to town to work on the car but Nick finished putting the wheel cylinders in and fixed a steel brake line that I messed up when I was taking the brakes out of the car. So great that he can do this!

Thursday was another day in town for me. All of the bays at the shop were in use so we couldn't put the car up. I spent an hour or two trying to get the brake booster out of the car. Some of the mounting bolts were rusted and it is not an easy thing to remove anyway. Part of the process means lying under the dashboard. I am a big guy and it's a small car. I was pretty crammed in there but got it out. The plan was to take the brake booster home and disassemble it to see what it needs.

I did that today. It was a challenge. The case was stuck shut by rust and gunk. I eventually got it apart, though, and cleaned all the parts I could get apart. Most of it looked really good once it was cleaned. There are a couple of rubber gaskets that need to be replaced for sure. The power piston is the biggest one and it is designed to move air, not brake fluid. The gasket on it is made of leather! Fortunately it's in good shape.

brake booster mostly taken apart

The brake booster uses the engine vacuum to assist in pushing brake fluid to the wheels. It's a complicated piece of equipment. I hope I can get it to work without too much expense. Buying a new one is out of the question. New ones cost almost $2000! If I need to get a rebuild kit I will have to spend just under $300. It is possible that I can find generic replacements for the rubber washers that I know are in bad shape. We will see how it goes.

Next week I will be back at the shop installing the new master cylinder, replacing the tie rod, and fixing the leaks in the oil pan and differential. It will take longer to get the brake booster done. If I am too excited to drive it we might bypass the brake booster. The car doesn't weigh much so not having power brakes should not be too big a deal.

My hope, before I started this big push, was that the car would be marginally drivable by this Thursday, which is my birthday. I am beginning to doubt that we can get it together in time but maybe?

Documentation Exploration

I found out through the 190SL Group forum that you can send away to Germany for a copy of the original build sheet for any Mercedes. All you need is the VIN number. So I sent our VIN to the Mercedes Benz Classic Center and the guy there sent it to Germany. A few days later I got a digital copy of the build sheet. There was a problem, though.

Everything is in German and the copy is quite faded and distorted. Remember that this piece of paper was almost 60 years old! Anyway, from what I could determine, this build sheet was for another car, not ours! It said that the car with this VIN number was a coupe, not a roadster, and that it was originally metallic gray with red upholstery. Ours should have been red paint with black upholstery. Definitely not our car. So I had to do more research.

wrong car!

It turns out there are three numbers associated with these cars. There is the chassis number, the body number and the engine number. Most of the time the chassis number became the VIN. On our car the body number was selected to be the VIN. I don't know why or how rare this is or if it is a problem. The car has been in our family since 1975. Probably not a problem.

Chassis number plate on firewall behind the battery

With 190SL's the whole "numbers matching" thing doesn't apply. With 190SL's the three numbers almost never matched, not even the very first cars. I read that. on the first two 190SL's made, the car with chassis number 5500001 had body number 5500002 and the chassis number 5500002 had body number 5500001. It really didn't matter to the guys at the manufacturing plant. Our car has a new engine in it so that number definitely will not match what was originally put in the car.

Body number plate on driver's side door jamb.

Our car's body number is 6502520 and the chassis number is 6503849. The first two digits depict the year it was made, in reverse. So the 65 means that it was made in 1956. The next five digits are the production number. In 1956 they built 4032 cars. Ours was number 3849 of that production year which would indicate it was made late in the year. The official production numbers from Mercedes aren't completely correct, though. Here's a link to a page that describes the production over the years and how Mercedes sort of fudged the numbers.

190SL's were hand built. Each body part has the body number on it, at least the last four digits of the body number. Only number-matched body parts fit together properly. On our car you can find the number 2520 stamped or written on the body parts. I even found it in chalk on the inside of the back of the driver's seat.

There is another chassis number plate mounted to the frame of the car. Above the plate, the same number is stamped into the frame below the voltage regulator. It is facing up so it can be really filthy with oil and dirt. I scrubbed ours off but you can barely make it out. Not an easy place to get to either. I couldn't read it at all just by looking at it. I had to use a flashlight and stuff my camera down there, take a picture, and blow it up in order to see that it is the same number as the plate behind the battery.

An unusual thing about 190SL's is the year the car was built is often not the year shown on the title. The cars were registered the year they were sold, not the year they were built. So our car is registered as a 1958 but it was built in 1956. I figure that it probably doesn't really matter as far as the legal stuff goes but it is important to know the year it was made to get the right parts.

When I registered it here in AZ, I didn't bother to try to change anything. I suspected that might turn into a bureaucratic nightmare. Still, it would be cool if, someday, I could get the title changed to show the year of manufacture and to have the chassis number be the VIN like most of the other cars out there. Or maybe it doesn't matter at all.

Now I have to bother the Classic Center again with a new number (the chassis number) and ask them to send to Germany for the build sheet that actually belongs to this car.

I will end this post with something much prettier than these dirty number plates and faded documents. I found a model of our car in a thrift store for $15. Cool, huh?

Lots of Little Details

One of the things I was dreading having to pay for was a headlight trim ring. The car came with only one and that was original with the car. It says Bosch on top of it. New ones are available but they don't have anything engraved on them and they cost $600 each. So, in order to have a matching set I would have to buy a pair or hope to find someone selling a used one that matches my other one.

There are two styles of headlight rings. The European style has a larger opening than the ones made for cars that would be sold in the U.S. After about a year of regularly searching eBay I found a ring for $65 and, because it was so inexpensive, I took the chance and bought it. That's when I discovered the details of the difference between Euro and U.S. trim rings. It was Euro. Wrong for this car.

I kept searching and finally found a correct, original U.S. trim ring on eBay. I made an offer, the offer was accepted, and I got a used headlight trim ring with the correct Bosch engraving on it for $300. It was in nearly perfect condition, too. So cool!

I got the re-sleeved brake cylinders back and have ordered and received the new steel brake line that I messed up. I really need to try to get the master cylinder out of the car but it is so hard to get to that I will take it to a shop in town with a lift. I am waiting for the shop to be ready for me. Another brake part I am a little nervous about getting into is the brake booster. This is a complicated bit of machinery that uses engine vacuum to boost braking. Fortunately I can bypass it until I am ready to tear into it.

I was missing the little arm that holds the hood open. After some research I realized that this hood support was just a piece of steel flat bar with a notch in it. I made one and installed it on the car. It worked great. Later, when I was looking through a box of parts, I found the original one. So I took off my home-made one and installed the correct one. So much better than holding the hood up with a board wedged in there.

I ordered and received the two missing parts from the horn ring assembly and put those in yesterday. I haven't tested it yet. While I was in an electrical mood I took some time and removed all the fuses from the fuse box and cleaned all the connections which had corroded over the years. It is good to have this done so I know that at least the fuse box won't be the problem when I get around to getting the lights working...... I hope.

I spent some time working on the doors. I found the clips that hold the fuzzy strips in place and installed them on the driver's side door. The window goes up and down between these strips. I cleaned and lubricated the window regulator mechanisms on both doors. There are a couple of missing bits before I can put the windows in. There are guide blocks that go on the front and back of the door glass. I have three of them and am missing one. I also need some thin felt strips for where the window gets bolted onto the channel that goes up and down. Once I get these things I will have windows that go up and down.

Last week I got the missing passenger-side metal false floor piece. It didn't fit. I had to trim it. This is because there are old sheet metal patches in the floor of the car that take up more space than the original floor panels did. Once I got it to fit I painted it black and installed it. Now the floors of the car are all ready for carpeting. I am not ready to order the carpet just yet. A carpet set for this car will cost about $650. That's pretty steep but I want to get the right stuff - German square weave. Not sure what color to get. I have been looking at photos of other people's 190SL's to see what they have done. The two most obvious choices are caramel or red. The upholstery is a caramel color - officially called dark tan. Most of the red cars with dark tan upholstery I have seen have dark tan carpet. But red might look cool, too. It would also show dirt a bit less than the dark tan.

There are some chrome trim bits in a box that I haven't been able to figure out where they go. Well, yesterday I figured it out. they go on the posts on either side of the windshield and they hold the rubber seals for when the windows are up. I spent some time cleaning them up. Also in the box was a bunch of weather stripping that was purchased for the car 30 years ago. I wasn't sure where it all went but now I know. Another mystery solved.

I started messing with the sun visors and with figuring out which little chrome piece is the center hold down for the convertible top. I am missing most of the screws for these so I will have to get new ones. The sun visors have green plexiglass in them. They are not in too bad shape but I also have brand new plexi if I decided to replace the original ones. Before I do that I think I will try some CD scratch cleaner on the old ones. Maybe that will clean them up enough that I won't have to go through the trouble of taking apart the frames on the visors.


It's slow progress getting this car together but it is happening. I read about a guy who was almost finished putting his car together and he had 900 hours in it already. I just need to keep plugging away at it.