2008 ML320 CDI w164 Rear Hatch Latch/Lock Repair

A common problem with the w164 chassis is the auto-pull-in electric rear hatch latch. These are known to fail, especially if the user operates the door without using the open/close assist hydraulic system (button/remote versus lowering by hand). The end result is a rear door latch that won’t open, close, or latch properly resulting in error messages and an unsafe condition. These little latches are very spendy and have gone through a few revisions. Not being one to give up easily and buy new parts, I wanted to see if I could have a go at fixing mine. The issue as I saw it first appear was that the door wouldn’t ‘pull in’ and fully latch. No amount of forcing would close/latch the door either so this was a safety issue worth fixing immediately.

I tore the rear panel off the rear hatch door, removed the three Torx screws, the emergency exit latch cable, disconnected the latch mechanism and pulled it out. What I found is below…a device that you must destruct to open and is not able to be re-assembled without additional ‘stuff’.

I despise plastic welds

I started by cracking open the upper ‘plastic’ case by removing the tops off the plastic welds. A myriad of parts were inside, hopefully able to be replaced properly without issue when I’m done. The bigger issue was removing the middle body from the lower unit, as there is a flag arm/cam that engages with the metal bits of the latch and this has to be indexed ~200 degrees around to pass through an ‘assembly slot’. They clearly made this device to only go together, not come apart. Some tinkering with a few probes and flashlight I was able to rotate the mechanism and fully disassemble.

Backlash is loose with upper cover removed
This interesting bit swings into action with one motor direction for pull-in latching but allows free operation of the mechanism once latched (so it doesn’t hang up on release)
More internal bits, the other end of the shaft on the left is missing something…

Lots of grease, complex components, but fairly well built. I started to poke around and found the issue fairly quickly, I had two pieces where there should have been one. I unstacked the gear train, spacers, etc and set them aside on a clean surface and extracted the closing mechanism shaft.

Well dang…

This item had a pretty ugly shear failure right where the shaft leaves the housing (and associated bearing support). That is a difficult fix as ‘gluing’ this joint would just result in an immediate failure. I’m going to need to add some strength, or build an entire new shaft out of something else. I opened to try the former.

Milling machine to the rescue!

I chucked the two pieces up in the mill and started removing metal. I also drilled the center of the shafts to fit a piece of drill rod for reinforcement purposes when it came time to assembly. This shaft needed to resist some pretty knarly torsional loads so I drilled deep.

Clean alumium

Tossed in the drill rod, did a dry test fit, and things are looking pretty good. Getting the bores perfect drilled/aligned was a challenge HOWEVER the gear that resides on the bottom (cam) side of the shaft has nothing specific about what it indexes with. The result was rotating the two halves before assembly to achieve the best co-axial configuration, making sure the two halves don’t push too far apart due to the un-clean shear.

Ugly but it might work

Now it’s time for the JB Weld. I mixed up a small batch of the Quick Set after visiting my friend in the middle of the night, me unable to find my stash of two-part epoxies. Little bit of helping hands later and confirming the coaxial rotations, I assembled and confirmed length against ‘expected’ length gathered from pre-milling measurements.

Time to dry

Once the shaft had some time to set up, I re-assembled the whole stack and indexed things back in their proper locations. The largest remaining hurdle was figuring out how to re-secure the upper housing plastic button welds that were now gone. I tried melting things but ultimately the solution was a bit less elegant.

Mercedes Latch Shibari!

The latch has been performing well for a number of weeks now, hopefully continuing to do so for quite some time. I have my eyes out for another broken latch assembly to repair and have at the ready if the need presents itself. While the construction of the latch is fairly decent, the serviceability is far below my expected standard for Mercedes hardware, though this is a Huf brand mechanism (the supplier for Mercedes latches/locks/keys).

Thanks for reading along!

w164 2008 ML320 CDI Rear Brakes Time!

After many weeks of “Brake Pads” warning on my city driver, it was time to install the new rear brake components I’ve been sitting on. On the docket were two new rear rotors, rear brake pads, and wear sensor.

Tire Removed, old rotor/pads

After removing the caliper, safely hanging not by the hose, pulling the pads, and removing the rotor retaining bolt, I pulled the rotor out and off the car. I compressed the caliper piston back in to allow for installation of the newer-thicker pads.

Rear hub, emergency brake visible
Rotor removed, pretty worn

I confirmed free movement of the emergency brake adjuster and blew all the loose dust/etc. out. This will enable me adjusting the emergency brake ones the new rotors are on. Inspected the old pads and wear sensor, definitely touching down. This wear sensor busted as I was trying to pull it before photoing.

Wear sensor into the metal

Comparison of the old pads and new, quite a difference. Note that the wear sensor isn’t installed yet in the new pads.

Got the moneys worth

Reassemble the brake system, rotor first and install the small bolt. I tend to put a small amount of anti-seize on the touchdown points on these because the wheel retains them and they’re only there to hold things in place and indexed while the wheel is off/loose. Additionally they tend to be VERY hard to remove. A little blue locktite works too.

Reusing the old bolt, yep.

Caliper back on next, compressing the piston to allow for the new pads is important. Push slowly, and sometimes fluid may need to be bled while doing this to prevent issues with up-stream ABS components. Checking out the caliper slides while here is not a bad idea either. These single piston calipers need to ‘float’ on the rotor to work properly. Here in the PNW our cars don’t get heavily salted so most of these components are good for the life of the vehicle if driven and maintained regularly. Check condition of hoses as well while here. Adjust the e-brake through a lug-bolt hole…tighten until rotor won’t turn then back off until just barely dragging. Confirm after doing both sides that the e-brake pedal engages near the top half.


Remembering to install and re-connect the wear sensor is important. Routing the wires where they will not get cut up or damaged by the spinning rotor is also important. Don’t forget the anti-rattle clip on the caliper when you’re done!

Thanks for joining in for what was a pretty straight-forward repair, documented for your pleasure.

Webasto AT2000ST Service Manual

Webasto AT200ST Service Manual (LIT9010439B)



Interesting note on this heater:

Recently ran some bad fuel through mine and unfortunately found out that the fuel metering pump does NOT like ‘thick’ fuel or algae running through it. These are often heater-specific fuel metering pumps and sealed units.  Acquired a replacement on e-bay and upon installing it found that the heater was throwing a glow pin fault code. Ran the diagnostics to find that the glow pin resistance was appearing ‘too low’ to the heater (even though it still turned glowing hot) so it would shut down.


I first found that there was a direct short showing between ground and the glow-pin source (through a FET to +12v). After analyzing the control module, I found a reverse protection diode had failed to short (probably the product of me trying to investigate the glow-pin operation and shorted/powered something). I replaced this with the reverse protection diode for the fuel metering pump and used a misc. SMD diode that I had on-hand to replace the failed one for the metering pump (a much less sensitively measured device). Now that the controller wasn’t seeing a short, I merely had to be concerned with the high (.6-.9ohm) resistance of the glow pin upsetting the controller. Book specifies somewhere around .4ohm.

I added two 21W light bulbs (an increased 2.4A load @ 12V…about 29W) and found that it didn’t complain about the resistance. I figure this fix will only last so long as the glow pin apparently is showing sings of giving up the ghost. Not very impressive for a heater that has less than 100hrs on it. The proper ‘fix’ if the glow pin is actually good (fault with the heater’s measurement circuit) would be to install a couple 15-20W 20ohm resistors in parallel to shed the load in a non-illuminating way.


Photos of the Webasto AT2000ST Control Module

The Journey – Burning Man 2011 – PDX to BRC

Throwing together a little account of the trip to BRC. Tune in later for the story of the return trip!

It was Friday evening, mid afternoon, and my wife and I had spent the past two days packing and finishing up the last minute projects. Fresh off of the high of NorthWest Mog Fest in Sheridan, OR and the associated shakedown run for The Ghost, we were itching to get in the drivers seat and put some miles between us and PDX. The drive to Black Rock City, NV for the annual Burning Man festival usually knocks out at about 10-11 hours in a ‘normal’ automobile. In a ~20,000lb vehicle that can’t push much more than 65MPH without death shake in the steering wheel, we were expecting to burn a whole day.

Departed that evening and make it about 100 feet out of the driveway. Power loss. Serious power loss. Got out, lightly adjusted the governor gap, and continued motoring. (In retrospect, I should have suspected the fuel tank restriction I have been fighting!). We pushed through some light I-205 and I-5 traffic and headed South to Newberg, OR. We needed to drop off the chickens and grab the last items from the house (my bike, some LMR equipment, etc.) I took the opportunity (while we waited for the temperature to lower outdoors) to adjust the brakes and give a final pre-journey inspection. I needed to grease the cam points on the rear brakes to prevent sticking on takeoff (ongoing issue). After freaking out that the adjustment created a bigger issue , which it actually hadn’t, I gave us the green light on the chassis and we departed.

We screamed down the freeway at a cool 63MPH, engine temps good, overdrive operating as it should, and Marley meowing in her box. We were headed to Corvallis, OR to drop off the cat before heading south. About 10 miles before the Corvallis exit, we lost the ability to go into overdrive. Engine temp was hovering around 180F so we kept motoring on.

Once we reached Corvallis, we ate some dinner (thanks to Barbra) and I started checking out the transmission issue. I read quickly though the manual and troubleshooting section and found that overfull/low can cause overheating of the transmission. I inferred that overheating of the transmission could cause the control pressure to drop (out of the hydraulic governor) and thus drop OD out of the range of the engine RPM. Using their method, I checked the level and found that it was HIGH. The easiest way to lower the volume and keep it clean, I figured, was to remove a pressure line (only 45psi) and put it into a milk jug to catch a quart or two of fluid. So I found a suitable line, disconnected it, and put it into a jug. I started the engine and milliseconds later was douched with hydraulic fluid head to belt line, including the street/tree/bus/curb/grass around me. Fortunately I had kept my hand on the shutdown switch even while starting so I shut the bus off within 2 seconds of the fluid bath (thank GOD for the electric shutdown…the old version required at least 30-40PSI air to shut down!)

After a few hours of cleaning up, and deciding that what was all over the place equated to about 1.5 quarts of ATF, I took a shower, bathed my clothes in liquid dish soap/hot water mix, and loaded up. We had called ahead and determined that the Fred Meyers (of which we had a 10 cent to gallon fuel credit) stopped fueling a 1/2hr earlier. Since we had just acquired about 30 gallons of fuel in Aurora, we decided to motor on and see what was available out by the freeway. Heading out 34 towards I-5, the overdrive engaged and we tore south since fuel prices were >$0.15 higher than other establishments I’d seen closed. I motored until about 2:30AM when I decided to pull it over and catch some rest. By this time, we were a little under an hour down highway 58 headed towards Kalamath Falls, OR. I picked a wide turn-out and crashed out with Emily, who was already asleep in the back.

After a very poor couple hours of sleep, I decided to hit the road again while there was still some chill air at the low altitudes. I motored on, stopping only twice for issues (one the fuel tank screen plugging, the other the overdrive popping out (and thus discovering a small coolant leak in the investigation). Power loss due to fuel restriction is VERY irritating mostly because the bus slowly drops speed (usually when you need the fuel the most) and in some cases, comes to a halt and stalls. The fuel tank screen clearing process was simple, mostly because we couldn’t drain the tank and fix it properly. The on-board air system of the bus had a nice 80-120PSI outlet on the auxiliary air tank that I had a hose and air nozzle to do tire fills, cleaning, or fix this exact problem. I removed the pipe plug just tank side of the fuel inlet check valve and blew all the crap towards the tank and off the screen. Buttoned everything back up and kept on zipping along.

At about 7:45AM, a short distance out of K-Falls (near the lake) I was surprised with a loud POW and the engine racing at much higher RPM. After doing a mirror check, fluid spill check, and gauge scan, I found the next turnout and had a look-see at what happened. It appeared that something had broken in the overdrive system and kicked us out of overdrive, at speed, under load. This equated to a VERY abrupt sudden shift while 500+lbs of iron slinging around at 1550RPM raced to over 2300RPM trying to catch up. Thus…the bang. While I was doing my checks, I found that quite recently the lower coolant hose on the transmission cooler decided to start leaking again where I had previously sealed it up with some Three-Bond and duct tape (classy…I know). With no hose stash, and being a long ways away from a parts/etc. store, I decided to make the same fix again and add some abrasion resistant material to the pipe so it wouldn’t happen again on this trip. Surprisingly, it held the remainder of the trip.

We rolled into K-Falls and hit the NAPA auto parts parking lot. I dissasembled the overdrive valve body and found that the Splitter Clutch Exhaust Valve Spring had broken in two, possibly related to the sudden shift. This spring was in-tact when I checked it in Corvallis, OR, so I rigged up some spacers and whatnot to attempt to regain normal spring length. (This never did function again even after 5 more adjustments stretching and spacing the spring to try and find the magic spot). I also purchased some hose to repair the transmission coolant hose if it decided to fail again. I wanted to also check the rear differential fluid so I walked next door to Autozone and bought a pint of 85w90 gear oil and borrowed a breaker-bar (1/2″ drive) to remove the pipe plug. Turns out the differential didn’t need additional fluid, so we motored on to the Fred Meyers fuel station to get fuel. 67 Gallons later, we pulled out paying about $3.83/gal for fuel (not bad!).

We departed the city and headed out across Eastern Oregon, Northern California, and Finally Northern Nevada. Our only stop as the Eagles Nest Resort (for some transmission tinkering and water fill-up). We departed there after some dinner and cooler air set in for the climb up the final passes before descending into Cedarville and onto the Black Rock Desert. We hit the 12-mile entrance about 7:30-8PM and rolled into camp about 10:00PM.

Overall the trip could have gone FAR worse, but loosing OD on the way down put a crunch in the engine economy. Fortunately it failed at the most ideal time, right when we started climbing hills and would have not wanted overdrive anyway. The Cedarville pass heading down wasn’t terrible as we  had clear roads and climbed most of it in 2nd gear (locked up torque converter) between 35-45MPH. Once we hit the last little bump at the top, it kicked us down to unlocked converter ‘1st gear’ and the climb was 18-22MPH. Temperature of the engine/transmission stayed cool enough that we just broke the pass at the 210F mark, and quickly cooled down as we rolled down the other side. The Jaccobs Brakes were a required piece of hardware for those passes and the result was little to no service braking needed for the entire grade. This is an outstanding feat considering many vehicles have overheated and/or lost their brakes going down these hills, only to end up in ditches or off the road. The noise of the jaccobs brakes was difficult to notice from the drivers area, and a medium rumble from the bedroom. We never had to use any emergency braking (either hand lever brake or spring brakes) and air pressure was solid for all climbs and descents.

For the PDX to BRC route, any air-brake equipped coach needs auxiliary brakes of some sort (magnetic, Jaccobs, exhaust, or some type of engine retarding. The pass out of Alturas into Cedarville and also the pass coming down into the desert just north of Gerlach, NV would be tricky. I cannot imagine the long decent at <20MPH burning air pressure constantly on/off the brakes. A suitably strong running diesel with a manually controllable downshift would also be suitable (dynamic braking). Check your slack adjusters, time your compressor to make sure it’s up to snuff, and get out your stop watch to do the decent brake timing. Google it.

A picture of the parking spot, for your pleasure.

Until next time,

Pre-Burning Man 2011 Crunch on The Ghost

Hey all,

Just wanted to outline (for myself and others) what was completed/not-completed in the pre-playa crunch on The Ghost Project.

Big Mechanical Jobs Completed:

  • Overdrive Transmission Installed
  • Spring Brakes & Associated Plumbing (Thanks Eric!)
  • New Cylinder Head (4-valve)
  • Rebuild Jake Brakes Installed
  • Tall Valve Cover Acquired and ‘Customized’
  • Black Water Tank Welded Up & Installed
  • Toilet Installed/Plumbed
  • Shower Floor/Drain Built
  • Bed Installed/Completed
  • Kitchen Countertop Finished
  • Kitchen Sink & Faucet Installed
  • Stove Installed
  • Refrigerator Mounted
  • Pressure Water System Built
  • Water Heater Installed
All of the above are the ‘big items’ that were completed and as you can image, had smaller subsets of projects that surrounded them (for example, all the body modifications required to make the larger transmission fit and connect up).
The clear most difficult task was the transmission mating/parts scouring/drivetrain setup. The head required some special rack components that we did not have to run the injectors, so there was a lot of futzing around there as well. The water system and interior bits just took a lot of time and in some cases, a bit of money to complete. I didn’t touch on the power system only because building a multi-voltage custom power system from scratch is not something that can be hurried though with the expectation of quality that I desire.
More updates later about our journey to come!

Generator Project Update

The generator (MEP006A) had a power-off failure recently.

Upon investigating, found that the exciter had received some serious overcurrent (melted the soldered connections on the diodes on the exciter winding) as well as may have fried something inside the excitation module above (big green box).

Need to perform triage and figure out what happened…but hopefully have this back online soon.


Upgrades thus far:

  • Replaced Primary Fuel Filter with Dual Element Glass (like on John Deere Industrial)
  • Replaced Secondary Fuel Filter with Single Element Racor Spin-On
  • Changed Oil
  • Changed Oil Filters
  • Checked Valves
  • Rebuilt Injection Pump (had bad seals on shaft and rubber coupler…very common)
  • Replaced bad fuel lines
  • Cleaned Connections on Fuel Pumps (problem area)
  • Serviced Cooling System (CAT Long-Life Coolant 50/50)

I am also working on building a tandem axle trailer just for this unit. The axles/rough frame was donated by one of the family friends Tony. Removed the decking (rotten) and narrowed the axles/frame by 1.5ft and shortened it considerably. I purchased new bearing kits, two new drums, four electric brake backing plates, and two new tire/wheel combos. I also purchased some upgraded lighting (LED all around) and trailer connectors/etc.  I got all 24V compliant lighting so I can power basic proximity lighting on the generator while it is running on a job-site or parked precariously. It will have a new frame horn (heavy duty) and unless stolen, jacking points on all four corners. I would like to do locking cable/tool boxes to store various associated items.

That is all for now! More updates when I find out what let the smoke out.