More B2 transmission woes

The other day, I was taking my 300SD to the store, and stopped in a gas station to fill up.  After putting in $70 of diesel I shifted into drive and heard a little clunk.  My immediate thought was that I left the fuel nozzle in the car so I jumped out and checked too see if I hit anything or of the nozzle was still in.  Everything looked normal until...I shifted into drive and it went NOWHERE.  Luckily, reverse still worked and I backed it into a parking spot while I figured out what to do with it. 
Now, when this happened I knew exactly what was wrong.  When I first got that engine and transmission (in the brown car) I replaced the B2 piston in the car, which is not a tough job at all.  I had also replaced the seal and old style metal bushing with updated parts from Mercedes.  Everything was working fine for about 30k and then this happened.  Unfortunately, mine was a bit worse than I thought - I actually broke the band.  Let me explain how the band works in the transmission. 
When you shift into drive (or one of the lower gears), the valve body engages the B2 piston via hydraulic pressure.  The B2 piston moves in and out, which pushes on a "pin", more commonly called a dog bone because of its shape, which seats in a receptacle on the B2 brake band that causes  it to engage when pushed in.  The B2 brake band piston is a common failure item because Mercedes originally used a steel bushing to seal the inner plunger of the piston.  It doesn't take a rocket scientist to realize that this would wear down the aluminum bore and piston due to it being a harder metal--so Mercedes released a nylon bushing design along with a couple new redesigns for the piston itself.  You also need the seal that holds the bushing in place (this is often overlooked) which went from a rounded shoulder to a square shoulder.  The seal is just like a normal wheel seal or oil seal, but smaller (I could not find one at Napa, had to order through MB).

Mercedes-Benz Transmission terminology for dummies (722.XXX series transmissions)
I find that a lot of people immediately go to the internet and ask "why is my transmission not working" only to receive a number of seemingly cryptic answers filled with letters, numbers, and foreign terminology.  Here is a quick crash-course on the most common terms and references when talking about these transmissions. 

B1 - controls 2nd gear.  A bad B1 band or piston will make the car shift from first to third.
B2 - most common failure in Mercedes transmissions for years, controls first gear, "shifting into drive"
B3 - reverse gear brake band.  Some models of MB transmissions can be adjusted externally to reduce slipping and flaring when engaging reverse, others do not have this feature.  If you have an older Mercedes with no reverse, the B3 is the most likely cause.  I see this especially in the gas w124s and w201s for some reason, many many cars on the market with no reverse.  This requires a trans rebuild to fix.
K1 spring - this is a spring in the valve body that controls the 2nd-to-3rd gear shift.  Over time, both the K1 and K2 springs wear out and cause the transmission to flare a bit between shifts.  There are "repair kits" available with new springs and seals for the DIYers, not a difficult fix.  These springs actually control how the corresponding clutches (called K1 and K2 clutch packs) operate.
K2 spring - similar to K1 controls the 3rd-to-4th shift, along with reverse and overdrive. 
"Flaring" - this refers to the RPMs spiking in between shifts under normal driving.  This is usually caused by either overly-soft shifts (worn out springs and/or vacuum issues).
"slipping" - This means the car goes in and out of gear, typically creating a jerking motion under acceleration, sometimes also a bad jutter.   
Vacuum tuning - The 722.xxx series transmission shifts are controlled by vacuum.  A line comes off the  engine and plugs into a part called the "vacuum shift modulator" on the passenger side, that will denote how firmly or how softly the car will shift between gears.  If you completely disconnect the vacuum line, shifts will be extremely firm (neck-snapping in my diesel!).  You can adjust the modulator by turning a plastic tee-connector on the outside of the transmission. 
Bowden Cable - This adjusts the shift points.  The Bowden cable is attached to the throttle linkage, and basically tells the transmission how far down you're pressing the accelerator...floor it and the shift points will be predictably higher.  This typically cable stretches over the years and needs tightening, which can be done on top of the valve cover at a white cable-screw followed by a rubber accordion cover.
Symptoms of a bad B2 piston -  If your piston is scratched or scored, it will "catch" on the outer bore of the transmission housing, bushing or seal.  This causes intermittent engaging of the forward drive gears.  Basically, you can shift into drive, but the second you put any load on the transmission  it slips.  You won't be going anywhere fast.  Many times a sticking B2 will turn into a broken B2 piston since the hydraulic pressure is extremely high, and scoring is only going to get worse (i.e. don't wait to fix it!). 
Symptoms of a bad B2 band - this is what I'm dealing with at the moment.  The piston itself is fine, no catching, marring, or scoring.  However, there is no spring tension on the B2.  I am able to push the piston in and it will not push out against my pressure - it should have quite a lot of pressure on it, so much that it is a difficult task to replace the outside cover without some sort of improvised "tool" jammed in between it and the transmission housing (I used a pipe the first time).  There is NO drive, no forward motion whatsoever.  To expand even more, you will not see a change in RPMs when shifting into drive, and not hear any hydraulic actuation under the car when you shift.  Strangely, when mine went, there was no debris in the pan indicating it was a clean break or the debris is stuck somewhere (very possibly the valve body). 

I am currently looking at a full trans rebuild (fully within my mechanical capabilities) but unfortunately I don't really have the space to do it since the car is in a friends' driveway and I am 250 miles away from home base where all my tools, stands, hoists, etc. are...although my trusty little socket set has gotten me pretty far before!

w126 ignition tumbler, not something to mess with!

I realize I haven't posted in a while here so I'm playing catch-up!  Here are some details about my ignition tumbler issues that I suffered about 2 years ago.

Here's what happened - my tumbler was "loose" but never had any trouble turning.  I figured I'd be a little proactive and completely replace the tumbler before it started wearing out even more.  Usually this is a super easy job, consisting of about 5 minutes of your time and an unbent paperclip.  Somehow, when I inserted the paperclip and turned the tumbler, it got completely stuck!  No movement either way.  This would be the same problem and solution for all of you who actually have had a completely stuck ignition tumbler as well, not just my folly.  Taking a look at the ignition face, there is no way to actually get the tumbler out without turning the key...unless you've got a good grinder and a drill!


1. Take out gauge cluster using the bent-coathanger method
2. Loosen bolts on the underside of the steering column and let it drop (gives about 1.5").  Taking off the steering wheel can help as well, but most of the time the retaining bolt is stuck on there with an ungodly amount of loctite and torque, I was unable to get mine to budge.
3.  Here's where it gets fun.  There's a little "pin" maybe 3/8" in diameter that holds the ignition assembly to the steering column.  It is part of the steering lock mechanism.  Some experienced folks on the internet have had success with punching this pin into the column with a drift, but I gave it everything and the damn thing did not budge.  Time to take out the dremel!  About 5 minutes with a tungsten carbide grinding bit and the pin was no more.  This step is much easier said than done.  There is almost NO room to work, and you need to get creative to find an angle that works.  I was able to slip the dremel in between the plastic steering column sheath (you can take this off if you get the steering wheel off) and the dash...a large socket was used as a spacer since there is some flex in both materials.  It was just enough to get the dremel bit in.  After grinding down the pin, you should be able to rotate the entire ignition switch mechanism within the steering lock housing.  
4.  With the ignition switch assembly freely rotating, it should slide out with some coaxing.  It isn't easy and still very tight in there, but I was able to get it out and have the igition switch dangling down below the column. 
5. Grind off the heads of the screws that hold the back portion of the ignition switch on (i.e. all the wires and vacuum lines side).  This will separate the actual ignition switch from the tumbler and steering lock areas.  It will also allow you to work on the tumbler mechanism on the bench and outside of the car.  Here is a picture of the stuck tumbler/lock assembly on the left and a new tumbler on the right.

6.  The plot thickens.  Since the metal ring around the tumbler was not moving, more grinding is in store.  Putting the new tumbler next to the old, I was able to figure out where the detent was in the ring and tumbler.  I cut the ring's detent lock around that area to free the old tumbler:

7.  More grinding.  I needed to grind the old tumbler's detent down so that I could more easily unscrew that hardened steel ring.  That was a pain, by the way--that steel is TOUGH and it takes a lot of cutting and patience.    You can see how the tumbler appears to have completely imploded and fallen apart.

8.  Finally, after much grinding and fitting, the old tumbler can come out.  Small victory:

The new tumbler went in easily!
9.  Reassemble, pretty much the reverse (minus grinding) of disassembly.  To get the ignition switch back together, I just tightly wrapped electrical tape around the two portions.  It lasted 30k miles until the car was parked with no fuss at all.  Even the steering lock still works somehow, the pin that I ground down was still slightly large enough to catch just a bit in the hole and secure the mechanism.  I imagine it could be removed with a punch now. 

Moral of the whole story is: don't wait too late to replace that sticking ignition tumbler!!

Fiber optics in the w126

One of the most frustrating parts of working on these w126s is the way in which Mercedes decided to light all of their console switches and instrument cluster.  Being high tech, they went with a fiber optic system that delivers light via an external socket.  Let me get more into detail here.

The two areas that people most often come in contact with these fiber optics is the instrument cluster and the center console.  First lets tackle the instrument cluster.  The cluster has long been a point of contention with Mercedes owners as these cars grow older, since the lighting becomes worse and worse until the driver (dangerously) cannot read the gauges at night.  Problem number one is the rheostat.  The springs that the company used in the rheostat fail pretty commonly.  This results in NO lights whatsoever.  I recommend jumping the rheostat, which consists of simply putting a  jumper wire between the two solder joints on the board.  If you want to do any LED modification or anything you'd have too do this anyways to help regulate the current.

The bigger problem with the instrument cluster is the delivery of light to the gauge faces themselves.  The bulbs are located in the back of the instrument cluster next to the blinker bulbs.  Easy to replace for sure, but if you look closely the light has to travel through crystals over the top of the plastic housing and then refract back down on the instruments.  In the bulb sockets themselves, about 90% of the clusters that I have seen have black charring (presumably from long time burning of bulbs, perhaps incorrect bulbs?) on the face of the fiber optic prisms.  I have also seen the prisms melted from having too hot of a bulb in there--obviously this doesn't help either.  In addition, all sorts of dust can get caught in there and is very difficult to clean.  My solution was to completely bypass the fiber optics in the instrument cluster and go with a homemade LED setup.  I mounted the LEDs where the prisms came out to light the gauges, and soldered them back to the bulb sockets.  The LEDs were actually far too bright so I had to shield some of the light with electrical tape...even that is still very bright, but that is my preference for dash lighting.

On to the center console.  All of the switches on the top of the console except for hazard lights --rear reading lights, defrost, sunroof, and antenna (may be more depending on options) are lit by means of fiber optic cables in back of the dash.  There is one light strand, much like a christmas tree wire, powering all the climate control and switch lights.  I believe these are wired in series so if one bulb goes out, the following will also go out.  There are 4 bulbs located in the climate control unit (I will get to that in a second) and one bulb reaches back into the firewall to a cluster commonly called either and octopus or a spider.  The fiber optic wires coming off of it go to each of the top switches, and one goes down into the shifter console to light the PRNDSL selection.  Conveniently, my octopus was completely torn apart by the previous owner who pretty much scrapped the whole interior.  After many hours of toiling I recommend just forgetting about it, you won't easily get those fiber optic cables back into the octopus--it is so far back against the firewall, it gives almost no room to work, especially for a precise placement of these wires.
Back to the light strand.  The first two bulbs on the strand light the left side of the climate control--the wheel and left couple buttons.  Then, the strand reaches back to the firewall where ONE bulb (stock bulbs are pretty dim) lights all of the switches and center console, then the next two bulbs return to the climate control to light the right flap buttons and fan speed/auto buttons.  Since I gave up on the octopus, none of my switches light up except for the hazard lights, and I replaced my climate control bulbs with LEDs to compliment the blue feel of the car.  Any questions please leave in comments section.  Thanks!

5 minute DIY - Installing a boost gauge in 300SD

Really, this install could not be easier.  I picked up a cheapo boost/vacuum gauge from Harbor Freight for about $20, came with about 3-4 feet of vacuum tube, a plastic tee connection, and some crappy bracketry.  Not only was it cheap, but it is extremely cheesy as well, allowing the user to select any number of colors to look super cool!  Being that my SD is already cool and particularly riced-out on the inside, this fit perfectly within the decor.  The easiest place to tap into the boost is with the overboost protection line running from a banjo bolt on the intake manifold over the top of the valve cover into a little cylindrical gizmo on the driver's side fender.  What this does is it monitors the boost and sends a signal to the ALDA which eventually regulates the amount of fuel going into the injector pump, thus limiting boost.  However, most turbos 30 years old are not putting out a whole lot of boost - thus the case for a boost gauge.  While you're working on the boost line, it is a good idea to unscrew the banjo bolt (don't lose it like I did last year...) and give it a really good cleaning.  They can get clogged up with soot and stuff over the years which will limit the performance of your car as well as render the boost gauge inaccurate.  Furthermore, it only takes 30 seconds of your time and is a good practice every couple years.
Anyways, regarding the gauge - I tapped in right before the overboost protection solenoid in order to give me as much vacuum hose as possible going into the cabin.  Unfortunately, being a piece of crap, the tee that came with the gauge broke almost immediately.  Luckily I had another tee on hand that fit a little better, and used that to tap into the line.  A boost gauge such as this requires the vacuum/boost hose to go through the firewall into the passenger compartment, and there are a few ways to do this.  The tubing that came with the crappy gauge was very thick and I didn't have any spare hard tubing available.  Therefore I chose  to route it in the same grommet as the hood  release cable, between the fuse box and fender.  There was a plugged space available (not sure why...), all you need to do is unplug it and route the hose through. A good trick is to stick an unbent coathanger in the tubing to stiffen it, then route it into the cabin.  That way, the flexible tubing won't bunch up and you won't have to crawl uncomfortably around the pedal area. 
You can mount the gauge wherever you please, but the most logical for me was right under the ignition tumbler, since it was out of the way yet still visible.  There is a trim piece that uses a screw along with a trim clip to secure against the top dash.  This was solid enough to mount the gauge.  I had some 90* steel brackets left over from an electronic drum kit I made, so I bent one to shape and screwed it in.  Attach the boost line to the back of the gauge and you've got a working gauge.  As far as wiring, I installed a radio at the same time, so I decided to use the 12V+ and illumination wires from that to also power the gauge LED.  The ground just went to a chassis spot.  In all, it took me longer to write this than it did to  install the gauge in the car.  Any questions just comment and I'll be happy to answer.

Pics are still coming.  I had written this a while ago, never got around to posting it, but unfortunately my camera is MIA :( 

DIY w126 cupholder part 1

There was a day back when cars actually did NOT have cupholders.  My Mercedes, both w124 and w126 like to constantly remind me of this fact practically every day.  Yet, there is a clunky pull-out ashtray and cigarette lighter that almost never works, go figure.  Let's exchange one for another, shall we?

Taking apart the old ashtray
Taking the old ashtray apart revealed a couple things...1 - that it was incredibly simply designed with a plastic tray and pop-up lighter on a spring.  2. The front wood was just glued on. 3. It was asking for a mod.
You can see that it simply slid on rails, here is the outer housing:

Therefore, you could make a thin board-like structure to slide in and out--this was the idea behind my design.  I wanted to keep it pretty simple, no metalwork, no hard cutting, nothing too crazy.  Here's what I've done so far:

1. Cut out a template from cardboard

Traced out the circles, I used a coffee mug as a template...then cut those bad boys out!  Here is the rough idea - it should look similar to this once finished (without the tear):

Next step was to cover everything in either fabric or fiberglass.  I had an old flannel sheet lying around and flannel happens to be PERFECT for this type of application.  A lot of custom audio guys use flannel soaked in resin as a base for custom speaker boxes.  It isn't perfectly flat, but will be decent once the resin soaks the fabric:

Next, mix up the resin/hardener to specification (1/10 can of resin = 1/10 tube of hardener) and thoroughly soak the whole thing, however not leaving any excess resin floatting around.  Stick a sheet of release paper (I use wax paper, it isn't too bad) under it so it doesn't bond to whatever surface it is drying on.  Here it is, soaked in resin:

Right now it is curing.  Part 2 will be following a good night's sleep and 8 hours of work. 

March check in - lots of good content coming!

March 1st check in!  I have been diligently working to get my diesel on the road.  Although I have to work full time and complete papers for school I've been able to get about 6 a day the past few days to work on the car.  I've been taking pictures as I go and they will provide for some more good DIY info.  Some of the upcoming topics:

- Boost gauge install
- Another radio install (this would be my 4th in MBs, lost count in other vehicles)
- Rust repair in wheel well
- climate control lights and the fiber optic spider/octopus.
- Slide out cupholder where ashtray was
- more custom back speaker deck pictures and resurfacing/reupholstering to match blue interior

W126 (300SD) custom 6x9" speaker and back deck install

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I wrote up this how-to for one of the forums, recently dug it up and realized how awesome this build was. Let me first start out by saying I'm an audiophile and there is nothing that annoys me more than poorly placed/EQd speakers and poor quality music. When I got my w126 (Boxy, 1982 300SD) I was surprised to see that it had a digital FM radio and four speakers with fader. Good for the time 30 years ago, but things have changed. The old paper elements were almost certainly blown or rotted, and tiny in size so sound quality would certainly be an issue.  Looking at the compartments on the rear deck (called a "hat rack" in the FSM) I realized I could squeeze a couple of 6x9s in there with some elbow grease.

Things you'll need:
- Big board of wood, MDF is cheap and easy to work with, which is what I used.
- spray adhesive (3M super trim adhesive, $10)
- wood glue
- hand-held jig saw
- drill (for jig saw start points)
- Fabric. I used Vinyl from Jo-Ann, pretty thick and tough stuff. I used 30 inches of it. (Picture 9) I got the color almost exact to the existing trim.
- 2 speakers. The ones in the picture are dummy speakers, old ones I don't care if ruined.
- speaker template will make your life a lot easier. I didn't have one so I tried using a grille from another 6x9, which worked okay.
- staple gun

First, remove the rear sear and take off the "hat rack" per FSM instructions (basically take off side pillar covers then lift the thing out). This was kind of a pain since it was in there quite snugly. Once that is out, get yourself a big ol' board of wood.

Take your back deck and place it on the board of wood. This will serve as your template. Trace around the edges with sharpie to get a rough outline of the piece. Cut it out (picture 1). It will take a number of tries and quite a bit of trimming to get it perfect, but once you do, it will look great! One note: I chose to place it OVER the trunk hinge, you can also cut a notch from the board but I thought itd look ugly.

1

Okay, so the next step is to figure out where you can place the speakers. I put them as far to each side as I could while still in the cubby holes. I placed a piece of paper over the holes, marked where the speakers were, then transferred it to my template. Fine-tune the placement (including symmetry and angle) of the speakers with the supplied template or grille and cut (measure twice cut once!!).

I decided to put spacers in to raise my speakers a bit. This was probably unnecessary but I didn't want them resting on the fuel tank. I simply traced around the speaker grille, measured an inch, then went around in the circle to connect the dots. (Picture 3) Drill holes, insert the saw, and cut away! Picture 4 is what I ended up with x2. Picture 5 shows them on the speaker.

2

3

4

5

After this, glue the spacers to the speaker holes, make sure everything is snug and where you want it (pictures 6&7). Let it dry a bit. At some point I thought it was a good idea to cut a hole in the deck for use with my subwoofer, which I have yet to install.

6

7

You're ready for the fabric! This is just like doing any car upholstry. I'll admit I am not very good at it, and it kinda shows. However, this isn't too bad, and the curves are all covered up by speakers! Anyway, stretch the fabric over the front. You could angle it at the spacers for a more "boxy" effect, but I chose not to. Use the spray adhesive to coat the entire front section, then apply the fabric. Use stuff to hold it down while it sets, and make sure there are no air bubbles. It dries very quickly so you have to work fast--hence why there are no pictures of this process.

Once it dries enough, turn it over and stretch it over the back. Staple it as much as you can so that there are no visible creases in the other side. Apply more adhesive if necessary.

Thats it!! Let the adhesive dry a bit more, throw it in the car, and install speakers! Picture 8 is the finished product with a few air pockets that need to be pressed out. In all it took me about 6 hours to do with trial and error, but the result is fantastic. When I get my subwoofer in place I will take care of the box air port I already cut (and re-glue the vinyl).

8

As for sound, even the dummy speakers are a vast improvement over stock. My only complaint about the sound quality is that there is not enough stereo separation, but only a minor complaint. As far as frequency setup, it is pretty good since the rear window deflects a lot of high frequencies directly toward the occupants.

I will be reupholstering this deck in blue to match the white car's interior.