Fixing a broken remote IR key fob with single button for Merrcedes Benz W140

Ever experienced that the remote IR key fob for the W140 have stopped working even after the batteries are replaced? This can generally one of two issues:

  1. The key fob needs to be synchronised again with the car. This happens due to loss of voltage on the chip when batteries are completely dead for a while.
  2. One component fall off due to old solder and mechanical stress over time.

Checking functionality and proper voltage

This is a very simple task. Point the IR towards your face and hold the button for one second at least. A red light will blink if the key fob works and the battery is OK. If not change batteries and look for the red blink. The battery type is 2x of CR2025 or CR2032 with 3V. If there is no blink, you need to open the key fob and maybe do some soldering. When the blink is OK, try to see if it can open the doors. If not, then it needs to be synchronised.

Here you actually see the IR diode becuase the camera picks it up. However with your eyes you will only see the red light blinking once at the lower edge of the IR diode.

Synchronising the key fob

This is a very easy job, make sure you have good batteries and the key will give a blink if you hold the button for at least one second. In order to synchronise it, go inside the car. Point the key towards the mirror and press twice at the button in rapid succession. Then within 30 seconds put the key in the ignition and turn it to position 2 without starting the engine. After you do this operation the key should be synchronised with the car, then you can check again if the IR key will close and open the doors. Retry this procedure if your are not successful.

Fixing loose components inside key fob

This is a bit more tedious and require you to do some electronics fixing.

Preparation

In order to do this job you will need a solder iron and some solder wire to fix it. Make sure you have flux cleaner after soldering to clean up the mess. To get the case open you need some small flat head screw drivers and a sharp and narrow knife to cut the glued case. For securing the case at assembly, you will need some glue. I can recommend Loctite 406 rapid super glue.

Loctite 406
Loctite 406 rapid super glue

Procedure

Now you have figured out that the key fob is not blinking a red light after you swapped batteries. So you need to open the key to inspect the electronics. The plastic key case is glued together and it needs a bit of fiddling to get it open. Follow the pictures below.

top side key fob
Top side of key fob
bottom side key fob
Bottom side of key fob, here is the battery lid located.
Flip open the key
Flip open the key
Take off the battery cover
Take off the battery cover.
Take out the batteries
Remove the batteries.
Use a flat scredriver to slightly pry open this side
Use a flat screwdriver to slightly pry open this side. stop when you feel a resistance. The other side is glued as well and do not try to pry the whole case open. It will break.
Use a knife to cut the opening
Use a knife to cut the opening this side since it is glued quite well.
Cut is open and free from glue
Cut is made and is now free from glue. It can now be pried open. Good luck!
Pry open the two sides of the fob
Pry open the two sides of the fob. Notice the push button component is totally loose from the PCB. This is our issue and why the key is not working. And probably the issue 95% of the cases.
Make solder pads on the PCB
Make some new solder pads on the PCB for the button on the PCB. Make sure not to get too much heat on the PCB and and clean the flux off with flux cleaner.
Solder the button back in place. Make sure the button body is firmly pressed to the PCB backing otherwise the button might crack loose when it is pushed next time. Make sure not to use too much heat for a long time that can damage PCB and other components. 380-400 Degrees °C is good enough.
Solder in place the button component
Assemble the PCB again in the lower housing. Make sure all other components have good solder.
Place spring in groove of the lower plastic case
Place spring in groove of the lower plastic case. Notice the angle of the spring.
Place button in key grooves
Place plastic tab in key grooves
Put the key in the upper plastic case
Put the key in the upper plastic case and align it with spring, then turn it around a full turn to tighten the spring so the key will flip out. This might take a few tries.
Key fob assembled
Key fob assembled. It will come loose without gluing, so you need to glue the case now.
Put a little strip of glue here behind the key
Put a little dab of glue here behind the key
Finish with some glue here one the other side
Finish with some glue here one the other side as well.

Now your key fob should be working again and not come apart.

Cheers, Robs out!

How to change Engine Oil and Filter in the M120 Engine – W140 S600

The W140 How To.. articles are too and far between, especially on this site. Gladly on my part (sadly for you guys…) there has been very little wrong with this car and there’s not much maintenance either since the S600 has not been used as a daily driver. The W140 appears to me as a very over engineered car with an extremely durable design. As mentioned in the review, it is quite heavy due to all the extra sound dampening and extra equipment for comfort. I have never been in such a quiet car ever. Rolls Royce is probably the only comparable here. But as any other car, it too require regular maintenance such as oil changes. So how do you change the oil and filter for the engine in the M120 V12 engine. Sounds a bit scary right?

Preparation

This Mercedes model was one of the last one without the common OBD2 interface, and it is not required to a use any electronic diagnostics tool to reset some car computer during the oil change. What you need though is a lot of oil, 10 Liters. Remember to get an oil filter too, please get a good German known brand since they will last longer, not disintegrate and not ruin your engine. The price is anyway insignificant at this point. You don’t want to cheap out here, trust me.

Another tip is to get 2 new air filter elements since you will be messing with the air filter box anyway. And since they are cheap and should be replaced regularly it is a good time to change them now.

What type of oil then? Well it kinda depends on the conditions used, warm climate vs cold, harsh driving vs. balanced etc. I am using the car mainly in summer in a moderately tempered climate and use the car quite balanced. So no need for high performance or very cold weather conditions. However the engine is quite large and is quite slow to get up to operating temperature, so a thin cold start oil is probably beneficial to avoid unnecessary wear and tear when the engine is running cold the first 5 minutes.

I have used Castrol’s recommendation chart and it recommended the 0w-40 Edge fully synthetic oil. This is not an ad for them, but easily available here. I am also a fan of Mobil1, where I have used 0W-40 SHC Synthese Technology.

Engine oil and filter - Mobil1 0W-40 - Mann Filter
Mobil1 0W-40 and Mann Oil filter

You will also need a special oil filter cap tool which can be acquired quite cheap from any car parts supplier. The cap is tightened to 25Nm and is nearly impossible to remove by hand. It’s also made of plastic so it can break, a new cap is not cheap. The trick here is however to get the correct one since there are hundreds of different ones. I spent quite some time to figure out the correct one without actually looking in the car and measuring. Firstly I couldn’t travel physically back then due to the lock-down and secondly I didn’t want to fiddle with the car just to find out the specs for the tool. (The oil filter cap is not visible by just opening the hood and requires removal of the air intake box). The oil filter removal tool is 74mm width with 14 slots.

Parts and tools

  • Oil filter (oil filter comes with new oil filter cap o-ring and a copper washer for the oil drain plug)
  • 11L of Oil, your choice, e.g. 0w-40 fully synchetic
  • Oil filter cap removal tool. 74mm 14 slots

Procedure

The oil removal process can be done with a oil suction pump inserted from the top of the dipstick tube and then removing the drain pan plug after, this makes less of a mess and is done in most workshops. However then you need an extra tool, so this guide will only use the drain plug method.

The engine should have normal operating temperature while changing the oil, since the oil will drain out easier, so take the car out for a drive before or plan to do the oil change straight after a trip.

S600 Oil dipstick before oil change
Oil dip stick before oil change. The car has run about 15.000km since last oil change and the oil is still very clear in color with a slight hint of brown. The engine has received zero refilling of oil during this time and is still showing max capacity. I’m very impressed.

Start by lifting the car up in the front and place it on jack stands in order to access the oil drain plug. Some of the w140 have plastic panels hiding the drain plug, so make sure to remove these. However my car does not have them and the drain plug is easily accessible. Before draining the oil from below, the oil filter must come out to allow better drainage. After opening the hood it can be very confusing locating the engine oil filter housing, and in fact you cannot see it unless you remove the left side air filter box. It’s well hidden below it.

Location of engine a oil filter housing on the M120
Location of engine a oil filter housing on the M120. Hidden below the left side air filter housing

Thankfully it is easy removing the air filter housing. It’s attached by two bolts and a couple of clips to the intake housing. You also need to disconnect one airflow sensor cable. Take care not to loose the intake hose clips into the engine bay which can be hard to recover, since they can come loose by themselves after loosening the air box. Loosing such a clip will make dirty air potentially enter the engine since it can then bypass the air filter.

Removing engine oil filter cap
Removing the engine oil filter cap. Almost impossible to unscrew by hand, so the tool is highly recommended.

After the left side air filter box is removed, you can now access the oil filter housing and remove the cap with the special filter housing tool. Use a joint on the socket to make the operation easier since access is poor down there. Pack a lot of paper and keep a tray on hand to avoid spilling oil when taking out the oil filter. Clean up all of the spilled oil, since it’s hot down there and we don’t want smoking and fires while the engine is running. Also use a small suction pump or syringe to get the little left over oil which lies in the house after the old filter is removed.

Oil filter housing M120 engine on w140
Empty old oil in the filter housing with a suction pump or syringe.

Then it’s time to open the bottom oil drain plug. You will need a large oil drip pan which can have at least 11 Liters. Beware the engine oil is hot and will come out with great force when removing the drain plug. Use plastic gloves to protect the skin and try to not loose the bolt into the pan when removing it. Expect about 10-10.5 liters of oil to drain out. It’s nearly impossible to drain it completely of 11 liters by just removing the plug as with most cars.

Draining engine oil from the M120 engine
Draining engine oil from the M120 engine.

When the oil has stopped draining after 10-15 minutes. Change the copper washer on the drain plug that comes with the oil filter kit, and the reinsert the drain plug. Do not over tighten since it will ruin the threads in your drain pan. Tighten the drain plug bolt to 30 Nm. It have happened a few times over the history that people have forgotten to insert the drain plug bolt and poured in the new oil which just lands on the floor. Do not stress and make this mistake!

New vs old oil filter
New vs old oil filter

Then replace the O-ring of the oil filter cap with the one that comes with the oil filter kit. Many recommends giving the O-ring with a coat of engine oil before assembly. I have no idea if it’s any useful, but I did it. It gives at least some less friction when installing the cap. On most cars it’s good to fill the oil filter hosing with oil so the first few rotations of the engine will have faster access to the new oil, but on this car it is not possible at all. Pouring new oil into the housing will just drain straight into the block. Also it is not possible to install the oil filter without it being attached to the cap itself, so there is no chance here.

The oil filter is installed by popping the oil filter to the cap and then inserted into the filter housing. Tighten the cap to only 25 Nm and it’s very important to not over tighten here since it’s made from plastic and easily strip threads. And a new cap is very expensive!

Drip pan bottom
Bottom of the drip pan. Inspecting for sludge and metal shavings can tell you a lot about the health of the engine. Here it’s all good and in good health.

Also inspect the bottom of the oil drip pan, look for sludge and which can indicate overdue oil change interval and metal shavings which can indicate excessive wear in bearings and pistons. In my case it was no such indications and all is good.

Double check drain plug and oil filter cap is secured. Before poring in the new oil you need to know how much to add so you’re not over filling the engine. Adding 10L should be enough, but measure before you pour the last liter in.

dd fresh oil using a funnel to avoid spilling oil all over the engine. After you have filled the quantity you need, measure with the dipstick and inspect it’s not above maximum level. Some of the oil will need to get into the filter and you probably have to add slightly more after the engine have run a few minutes.

Refill engine oil
Refill engine oil into the M120 Engine. Oil capacity 10L

When starting the the engine, make sure that you get good oil pressure quite fast, and inspect for leaks in the drain pan and around the oil filter cap. After the engine has run for a few minutes, turn it off and measure the level with the dip stick again. Add oil if necessary, but do not over fill. If too much is added then you need to remove the excessive oil with a suction tube.

Reinstall the air filter box. Now It’s a good time to also change the two air filters on either side of the engine. No tools required here, it’s made like a drawer, just like how you store your underwear and socks at home.

Then take a short drive of 5-10 minutes, see that you have good oil pressure and that the engine feels normal. When coming back home, inspect for leaks around the oil drain plug. And remeasure the oil level with the dip stick, add a bit oil if needed. Then you are done for another 10.000-15.000km.

Robs out!

How to change the front shocks and sway bar links in Mercedes w140 S-Class

Changing out worn shocks might be most effective and cheapest fix that can transform the ride handling of your car for the better. My S600 had very noticeable up and down wobbling when driving over bumps and a quite large body roll making in tight corners. It was becoming a bit boat like there at the end. The S600 is a very heavy car and needs good handling when going fast. A flatter ride in corners also makes for a more comfortable drive overall, so your passengers don’t wake up from their naps.

Changing the shocks will reduce wear on other more expensive suspension components like bushings and tires, while overly worn might damage the suspension. Changing the shocks is in your interest to be an economical DIYer.

The front suspension uses normal a McPherson setup with separated gas shocks detached from the springs and can easily be removed. The rear suspension on the other hand uses the more complicated SLS leveling suspension setup and don’t use shocks at all. Instead it uses hydraulic rams along with pressure spheres. More effort and money is needed when doing maintenance on the rear suspension than the front. The SLS however normally lasts a lot longer if you remember to change the fluid once in a while.

When changing the shocks you should also use the opportunity to inspect/change some other wear items easily accessible in the front suspension. This could be sway bar links or the brake rotors and pads. The sway bar links wear down faster than the other suspension components due to their tiny ball joints and should be replaced whenever cracks appear in the sleeves or any slack starts to be noticeable. Worn sway bar links can make annoying sounds for you and your passengers. We all know expensive cars are known for being the most squeaky cars around, let’s change that!

Preparation

You should expect to use around half day to a day on this job, depending on your skill set, the amount of rusty bolts and your tools at disposal. It’s something you can do easily on a weekend. When doing the job I was even under time pressure since I had to catch a flight the same day. I managed to catch the flight and get the job.

If you want to bundle more front suspension jobs while doing the shocks, I recommend removing the front wheels and inspect the suspension such as the sway bar links, brake pads and rotors as well as the tie rods. Any more advanced jobs than that you will will require a lot more time invested so be sure to plan accordingly. Usually large front end jobs require a re-alignment of the suspension, but is not required here.

Parts needed (as described in the article):

  • 2x front shocks. I recommend premium brands such as Bilstein or Meyle
  • 1x Left front sway bar link
  • 1x Right front sway bar link

Tools needed:

I ended up using quite a tool collection because of rusted bolts on the sway bar links, but this might not be the case for you. I think this collection of tools goes into most home car mechanics tool box, but there might be a couple of them you should consider getting. Always better to be prepared than sitting there stuck without finishing the job.

  • Jack and 2 jack stands
  • Socket set
  • Long breaker bar
  • A set of long spanners
  • High quality hex sockets
  • Torque wrench
  • Hammer
  • Rubber/plastic hammer
  • Pin punch driver
  • Locking pliers
  • Long Hex keys
  • Propane blow torch (super handy when things are stuck)
  • XZN (12-spline) sockets (super handy when Hex nut gets rounded off)
  • Blue thread lock (for brake caliper bolts)
XZN socket set
This is how XZN Sockets looks like. They are always a savior when hex bolts gets rounded off.

Procedure

Start by raising the front of the car and remember to use the E-brake together with wheel stops. Place the front on jack stands. I also like to keep the jack in the up position as redundancy on the side I’m working with. You can lift the w140 with the jack on the rubber jacking pad and place the jack stands more towards the center of the car under the sub frame.

Jacking up a Mercedes w140
Jacking up the w140 with a garage jack and jack stands. Notice the rubber pad location is used with the jack and the jack stands are placed under the sub frame. Always use some padding between the car body with the jack and the jack stands, such as hard rubber or some wood to protect the under body from rust.

The shocks can be removed when the calipers are in place, but to remove the sway bar links, both the calipers and the brake rotors need to be removed to access it. I will first describe how to replace the shocks since it is a much easier job. Then I will describe how to replace the sway bar links.

Shocks

Start by removing the lower bolt. Use a long breaker bar and a large spanner to break the bolt loose. Then move to a ratchet to get the nut off. Use the jack to lift the lower suspension arm a little bit to relieve some tension in the bolt through the bracket hole. Then use a punch to smack out the bolt with a hammer. Be careful if the bolt catches too much, then try to relieve more pressure before continuing. Most shocks do not come with replacements for the lower bolt and nut, so try keeping these in good shape.

Removing lower bolt on damper
Remove the lower bolt on the damper.

When the bolt is loose, open the hood and locate the top nut. The top part of the damper can look different from each other. You have to keep the strut bar still with a hex socket or flat pliers while using a spanner to unbolt it. There exists a special tool to do this with a socket, but is frankly unnecessary except if you’re addicted to tools. This locking nut always comes with a replacement nut and you should throw away the old one. When the locking nut is off you can easily remove the old damper.

Location of top part of damper under the hood
Location of top part of the damper. This old damper uses a hex setup for keeping the damper still while loosening the locking nut.

Before installing the new damper, push it completely down a few times to relieve tension. The installation orientation has no influence if the brand does not specify it. Start by installing it with the top part and the top locking nut. When installing the new damper you must take of not letting the damper shaft rotate while turning the locking nut. Keep it secured while fastening the locking nut. This is to reduce the risk of breaking the internal seal of the damper so it will start leaking. The nut does not need to be extremely tight, but do tighten it until you feel it is secure. It is very important to make a re-tight after the car is on the ground. I will remind you of this again shortly.

Now you will probably notice that the new damper is quite shorter than the old one when you took it out. You therefore have to compress the spring by jacking up the lower suspension arm until you can align up the bolt hole. This might be a bit tricky and use a hammer to punch the bolt through since it is nearly impossible to align them up 100%. Again take care of not ruining the threads on the bolt. The lower bolt and nut should be torqued to 80Nm.

Front shocks w140
Old Vs New shocks. Notice the old one even leaks oil!

Front sway bar links

Now on to the more fun part where you can expect to meet more of a challenge. First you need to turn the wheel you’re working on all the way out to get access on the backside. Start by removing the caliper, it is held by two bolts. You may require some force to break them loose. Prepare some method too hook the calipers up in the spring to relieve tension on the flexible brake hoses. Never let them hang freely. I used long zip ties here and I could just to cut it off when done. But a simple S-shaped hook would have been even easier!

Front suspension and caliper
Turn the wheel out completely before starting.

The caliper might be difficult to get off if the brake rotor has a lip on the edge. Use a pry bar or the back side of a hammer to press in the outer brake pad by using the rotor for leverage. Be careful not to damage the pad material. When the caliper is loose, secure it up onto the spring.

Location sway bar link w140
Location of sway bar link. Notice only one accessible bolt. The other one is behind the disk rotor.
Brake caliper w140 removed and hanging
The brake caliper is remove and secured in a zip tie from the spring to relieve tension in the flexible brake hose and brake caliper sensor.

When the brake caliper is loosened you can start remove the break disk rotor. It is secured by a tiny hex nut, but you might find this lost or broken. Mine was broken off on the right side, but the left one was fine. Loosen the nut with a hex socket. If the brake rotor is sticking to the hub, try hammering gently on it with a plastic hammer. If it does not pop off, it can be quite frozen due to rust and you’ll need heat to loosen it. Ignite up your blow torch and heat the area just around the hub. This should expand the rotor just enough so it will pop off with a light hammer blow. Over heating the hub might make the hub grease melt and run out, so be careful with the heat.

Brake rotor locking nut w140
Brake rotor locking nut with hex. This might have broken off already.

Now it’s the time to locate the outer sway bar link nut. Cross your fingers for no rust. It is located right under the brake rotor. The locking mechanism is not the best engineering, since you’ll need either a special tool or trying to combine a socket with some magic tricks. I used a socket, secured it with locking pliers and then used a hex key sticking through it. After some fiddling I managed to get the nut off. You can usually loosen the bolt the first few turns by using just the socket normally.

The upper nut should be the easier of the two to get off, since the lower one usually gets all the rust and is easier to round off the hex bolt head. Soak it thoroughly with rust penetration fluid and let it work for 15 minutes. Then use a hammer and whack that nut good a couple of times.

Removing front sway bar link nut w140
Removing the lower sway bar link nut. Cross your fingers that the hex will not round out. I only got a 50% success rate.

I got lucky with one side, but the other side I had to drive in an over sized XZN socket with a hammer so it’s surely stuck in there. Then I could get enough torque to loosen the rusted nut. This will obviously destroy the part, but it’s thrown out anyway. Unfortunately I did not get any pictures of this process since I was struggling a bit and running out of time.

Broken sway bar link sleeve
The sleeve was broken on the sway bar link. This does not take long until squeaking starts!

Now you should be able to remove the sway bar link. Go fetch the one that fits depending on the side you are working (hopefully you order the correct ones). Fit the top side first, then you move on to the lower side. It can a be a bit tricky to fit the lower side onto the sway bar again. Get a long bar or a long spanner and wedge it between the spring to get leverage to push down on the sway bar.

Use leverage to fit the sway bar link to the sway bar
Use leverage to fit the sway bar link to the sway bar.

It is not necessary to tighten the sway bar links very hard, just snug with enough force so they sit on. Remember these will probably rust tight faster than you can say cheese and the hex bolts will round off again.

old vs new sway bar links
Old vs New Sway bar links.

Caution: Before assembling the rotors, make sure you brush off any old rust off the hub face and the inside of the rotor. This is to prevent rumbling while braking and that the rotor sits on straight! You can use a steel brush and a rough pad to do this. Also brush off any surface rust on the front side of the rotor where it meets the wheel.

The front caliper bolts need a layer of blue thread locker on them since there are no shims or similar. Use 115Nm torque when tightening the caliper bolts.

It can be a bit tricky to mount the wheel if the little rotor locking nut is missing, so a replacement might come in handy here. Otherwise you have to align the hub with the rotor first and then with the wheel when sticking in the bolts.

Now I hope you will take on this task without paying stupid amounts of hours for mechanics to figure this out at a workshop. Go do it yourself!

Cheers, Robs out!