HumberSS

So my experiences with the w163 span most models, including both the v8 and V6 petrols and the diesel 2.7 common rail. Largely the petrol models are fairly simple reliable things out of the box. All models run the 5 speed 722.6 trans, which is used in a heap of mercs of the era. It largely gives few problems if serviced well. They are meant to be a 'service free' trans. Don't buy that bullshit, fresh oil and filter does wonders. One issue that does crop up is the low range selector motor electric motor can seize, necessitating either the bash with a hammer technique, a pull apart and fettling of the contacts, or a replacement.

The V6 M112 engine isn't really much to write home about as it uses nearly the same amount of gas as the v8s M113, so why bother... They are effectively the same engine with two cylinders lopped off so share a lot of parts in common including water pumps etc. In nz I think all models are rated to tow 3200kg braked.  

Other general issues are around the radio chip in the key failing, requiring recoding a new key. I've never had this problem. Also something called the All Activity Module, which is sort of a central brain. I've never had that fail either, but they can cause some dicky little issues. It would be great if someone made some sort of emulator to delete this, it would sort a lot of little bugs. Window switches as mentioned above. Lots of cheap knockoffs on AliExpress for cheap - along with many other parts. The door locks can sometimes be problematic too. They have a weak spring in them which breaks and the locks fault. I've never replaced or repaired these...not bothering locking my car I found was the easiest fix.. they are a cunt to remove so I gave up, haha. Like all vehicles there are other things that can fail all over the show but I haven't experienced much else there, and what I'm outlining here is the common stuff. Oh the odd bit of trim falls off, my solution there was often not to replace or use some boogie up to fix...

My main area of focus has been around the diesel engine. It's a solid unit and makes a healthy 121kw out of the box. My first one went like a cut cat, my current one has been remapped to 150kw to achieve the same thing by some random eastern European YouTuber, Caryfuk8 I sent the file to. I used a cheap AliExpress Kess clone box for sucking the ECU file off and he did the rest. Dark art that shit, I don't know how to write a map..

his intention is to get a 0-100 in the 6 second bracket on largely stock hardware, which he has very nearly managed. He mapped mine to 20psi, I didn't want to roll coal, and he put in a hard cut which sounds awesome.. example here.

before undertaking a map, there are a few hardware issues to sort with the 270. Underneath the complicated things is actually a simple bulletproof engine. The trick is to get rid of a lot of shit up front so it doesn't cause you grief, as much of it will at some stage. I know a local Dutchman here who's pretty clever with them and he has one that's seen over 900,000km. So yeah...

The main problem with Merc common rails, and probably a few other common rails is a thing called black death. The injectors hare held down by a cantilevered forked bracket by way of a stretch bolt. It is truly a shit design. Over time the injector seal to head becomes compromised allowing a slow built-up of diesely sludge around the injector. Bad ones will chuff and damage the sealing face on the head. Sometimes removal of really bad ones will result in snapped bolts (I've had this problem). I've found that it's best to pull all the injectors and clean seats with a bit of scotchy on the end of a screwdriver, or recut the faces with a cheap AliExpress seat cutting tool. Also cut a groove in an old bolt and use to fastidiously clean threads with solvent etc to ensure correct torquing and bolts no bottoming out on old sludge..Replacement with factory Merc seals or aftermarket is generally fraught. New stretch bolts are always required. One fix is to use a Honda diesel washer, and annealing it to soften it to allow better crush. The Honda washer has an oval cross-section so you get proper point contact. During lockdown I tackled mine and due to limited oversease shipping I couldn't get the Honda washer, so I resorted to making my own. I brought stock Merc washers, which are flat and hence useless. I lathed up a little press tool that I then fit the annealed washer into and smacked with a hammer. The press tool was shaped to effectively compress the inner and outer diameters of the washer and raise a peak in the centre on both top and bottom faces. I then reannealed the washers before fitment to soften and allow 'crush'. These are presently over 50,000km deep and no sign of leaking. Furthermore Merc updated the torque spec on these to 7nm +90deg +90deg, formerly it was only one 90deg. It's a shit design and it feels like it was designed to fail, the cleanup is a patience game but once you sus it they can be pretty reliable.

Once the injectors are sorted the other main issues largely revolve around the egr system and the inlet swirl flaps. The swirl flaps are to increase low rpm air speed, but they sometimes fall apart and get lodged in the inlet tract, or leak around the pivots, or seize up, ironically due to egr sludge buildup, causing the actuator motor to fault and throw a limp condition. So the trick is to simply remove the manifold and get rid of the flaps and drill/tap/blank the pivot holes in the plastic manifold then clean all the exhaust sludge from the manifold from the egrs most positive influence over emissions.. if your swirl motor is still working just leave it plugged in. If it isn't you can put a resistor across the plug so the computer thinks it's still there. Lots of internet info on this mod. 

The egr system also needs to go. This can either be mapped out, as can most things including swirl motor etc, or you can splice a little diode/resistor combo in to the ECU inputs to trick it. A lah below..

Again. Computer still thinks it's there, it's basically emulating a difference in airflow condition that the computer wants to see. I also physically removed all egr stuff and made a blanking plate on the head by number 5 cylinder, which only has a water outlet to hook to the heater. I also remove the fuel heat exchanger while I'm at it as it's only useful in Russia and Nordic countries where it's arctic cold. Makes life easier.

Only other mod I've done is add a bigger variable vane garret turbo off an e320cdi om613 3.2 6 cylinder. It was bolt on and only required some exhaust mods, removing the cat. I actually lunched the first turbo due to not fixing a dodgy turbo inlet pipe and bits got sucked in...

Aside from that there is not much else. It seems like a minor laundry list, but if you buy one knowing these things from the outset, it's about a 2 day program of work as a baseline to get rid of a whole lot of future niggles that have a good chance of cropping up. 

Knock off parts are really cheap. Probably due to Russia's proximity to China. Ball joints are about $40 a corner and can be fit in 20minutes on a jack for instance. Bumpers are made of something akin to glass, and owing to my roughness I have disintegrated both ends of mine and replaced with steel buttyness.

Any questions feel free to ask. I'll move on to the start of my GL320cdi adventure next...

So there is some shit to know about the w163 platform. Firstly, they are the only Merc on a full chassis, or body on frame, aside from the G-wagen. They were originally slated to replace the G, and we're actually launched as a concept car in Jurassic Park movie (circa 1997). They are much loved by the Ruski's, most of europe, Asia the USA, and Soccer Mum's. They kind of invented the SUV category in a way. They are very safe and have many stability features and 12 airbags. Merc was broke at the time and half owned by Chrysler so the engines ended up in everything. Think Jeeps, Ssangyongs, ambulances and sprinter Vans erc. They run independent susp all around, torsion bars in front and coil over rear, yes they can be lifted both at suspension and body off frame. They have a low range transfer case with a very low crawling gear. They have exceptional departure and approach angles, still ahead of many more contemporary machines. They have a 20" fording depth factory. They have massive 4pot brakes and a very clever 4wd system in lieu of locking diffs. Basically they brake the slipping wheel which transfers the power to the non slipping wheel through the open differential...it all happens very fast and is quite effective. Toyota has only just copied this on the recent Hilux.. I suspect it's due to a patent. They were built in Alabama, Germany and Japan. The pre 2000 models are best avoided as they facelifted and fixed a lot of shit around 2000. They ran till about 2005. I'll mostly give my experiences with the 5 cylinder common rail. Sorry for few pics to accommodate my technical foibles, but there's loads of internet info, should you be so inclined. Or ask here. Some things I have had to solve myself.

Cool Merc development vid...

https://youtu.be/f599FIqCpSg