How to remove the M110 engine from W126/W123

If you did enough work with cars you end up some day with the need of removing the engine, the very heart of any car. Think of it as heart surgery, but not entirely so complicated. Actually quite easy compared to many other car related tasks, but it’s a long job if you venture down this road.

So how do you take out the M110 engine from a Benz? I’ll teach you the dark arts of car surgery so stay with me in this dreadfully long post.

Always leave the transmission on the engine when pulling it out..


If you have either w123 or w126 the procedure is almost the exact same. The complication will be if you have an AC or not and small difference in wiring and placement around in the engine bay. Usually the bigger the engine the more difficult it is to get out since the space gets really tight and hard to get to places when removing stuff.

If you are doing major engine overhaul or need to do something with the transmission, it is best to just take out the engine with the transmission. Always leave the transmission on the engine when pulling it out even if just doing engine work.


Preparation is key like most things in life. Don’t plan to use your car in the next few days, or a week if you are new to car fixing. Taking out the engine can be done in under a day and putting it just takes a bit more time. This is definitely a job where more people can be helpful, so go get your buddies and offer them some beers.

You need to acquire an engine lifter also called an elephant jack, and some good quality lifting chain and shackles that are rated for some hundred kgs (I think the M110 is not heavier than 300kg, but you have to cross check that since I don’t have the exact numbers). A very nice tool to have is an engine tilter which you can hang from the lifter. It will make your life easier since the engine needs to get out of the engine bay beam at a very tilted angle, but it is doable without. I made it without, but it required some wrestling and tryouts with different chain lengths.

Other than that you basically need some jack stands and a basic socket tool set, and of course patience which is found at the bottom of the beer glass.


NEVER crawl under or have any body parts like your arm, or place your friends under the hanging engine and crane while lifting the engine. Then you won’t come at harm if the lifting mechanism should fail and the entire engine come smashing down. The engine will be needed to be lifted quite high to get over the front support beam in the engine bay and you must take lifting heavy objects very seriously. Also try to minimize the time of the actual lift, not leaving the engine hanging, but setting it down as fast as you have it outside the engine bay. This will minimize the time of potential hazards hanging from the crane.



The first thing you will do is to remove the battery and start to drain engine fluids. You will be removing oil and coolant hoses connected to the engine. Start with the engine coolant, open the heater switches to full heating then drain fluid via the radiator drain and the engine block drain. Check out How to do a coolant change on the M110 engine. Remember to put the caps back in in order to not loose them and to prevent dirt from entering the system.

Then drain the oil sump. When it has drained disconnect the hoses to the oil cooler next to the radiator, lots of oil will come dripping out of here as well so watch out.

It is not necessary to drain out all the automatic transmission fluid if you do not plan to do any transmission related job.

The third liquid to drain is the power steering fluid. Open the power steering reservoir cap and suck out the oil with a oil sucking pump. When empty disconnect the hoses to the power steering reservoir and be ready for more of this oil to come leaking out of both the reservoir and the steering box. Sometimes the hoses can be tricky to get off while the engine is still in the car. I could only get one off and had to connect the second hose when the engine was lifted slightly up.

power fluid reservoir w123
Suck out the power steering fluid

If your car has an automatic transmission, the fluid is also cooled via the lower radiator and connected with two flexible hoses. It is not necessary to drain out all the automatic transmission fluid if you do not plan to do any transmission related job. Instead, when the car is standing level, disconnect the two flexible hoses from the hard lines which transports the fluid to the radiator. Some fluid will come dripping out, mostly from the radiator. Carefully clean the tips of both hard lines, then cover them securely with duct tape sealing the holes to prevent more fluid to leak out and preventing dirt to enter. This way you are not needed to drain the automatic transmission fluid which takes forever.

transmission cooler lines w126
Disconnect the transmission cooler lines.

After the fluids are drained, start by removing the engine two coolant hoses connected to the radiator and all heater hoses connected to the chassis.

removal of lower radiator hose w126
Remove the lower radiator hose.
radiator hose M110
Disconnect the radiator hoses and and it should look like this when the top ine is removed.

After the hoses are disconnected, the exhaust is needed to be removed. I really dislike this part since it involves heavy and big parts. Now you need to raise the car up on jack stands for access. I personally use ramps for the front wheel so I can just drive the front up, and then raise the back end up on stands. For me this is much quicker. If you have a car lift, then bless you sir.

disconnecting heater hoses W126
Disconnect every heater hose you can see that is attached to the engine.

With car up on jack stands, the exhaust needs to be loosened at the manifolds. You only need to loosen four bolts when you have the twin pipes, but they can be a pain in the butt since they always are rusty due to the heat.

exhaust pipe removal w126
Disconnect the exhaust pipes from the manifolds.

When the manifold bolts are loosed, support the front end of the exhaust from under the car before you loosen the exhaust support that is on the transmission. Now the exhaust is only hanging by the rubber donuts at the back and sitting on the support at the front. One last thing to loosen before you remove the exhaust, is to completely is to remove the starter motor ground cable, which the exhaust pipe can get stuck at when you try to drag it out from the back of the car.

starter motor ground cable M110
Loosen the starter motor ground cable.

When the starter motor ground cable is loosened, lower the exhaust to the ground with removing your front support and removing/ cutting the rubber hangers. Be careful so it doesn’t fall on you since the exhaust system is very heavy. You should have some help when removing the exhaust system. Finish by dragging the exhaust out from the rear of the car while rotating it sideways so the front pipes don’t get stuck.

Also make sure the automatic transmission is set to neutral to prevent stresses internally if the transmission is set to park (the flex-disc bushing bolts are usually set to very high torque..

Now with the exhaust removed the fun part starts. The drive shaft has to be disconnected from the rear of the transmission output. First remove all the aluminum heat covers under the car. Block the back wheels from turning, by handbrake or the pedal brake or whatever, this to prevent the shaft from turning when you loosen the bolts. Also make sure the automatic transmission is set to neutral to prevent stresses internally if the transmission is set to park (the flex-disc bushing bolts are usually set to very high torque + corrosion). Loosen the drive shaft collapsing bolt first, which is located just in front of the center rubber bearing. This way you are able to collapse the drive shaft and remove the front part from the transmission later. Before removing the flex disk nuts, it’s a good idea to remove the transmission back support plate to get greater access with spanners, just remember to support support the weight of the transmission with a jack, slightly raising it so it won’t fall down when you remove the plate along with the rubber mounting to the transmission. Then finish by loosen the 3 flex-disc nuts that are connected to the drive shaft. The other three nuts you can leave in and the flex-disc will stay on the transmission while pulling out the engine. Check out How to Remove the Propeller Drive shaft.

Hopefully you managed to loosen the front drive shaft without too much effort and being strong like some 80s hero. While you’re already under the car, it is a good time to disconnect the three control wires that are connected to the transmissions along with the shifter rod. Place them out of the way of the transmission so they will not get caught or stuck later.

automatic transmission cable w126
No tools needed for this on, just pull it out.
automatic transmission cable w126
The cable is secured with one bolt.
automatic transmission cable w126 w126
The cable has a plastic locking system which you have to turn first and then pull to get it out.
Mercedes w126 transmission shifter bushing
Disconnect the shifter rod from the transmission. Here the bushing is so worn and dried up that I would never reuse, replace at any circumstance when this worn. Since the car actually disengage the park gear when the car is parked!

When you’re done with the transmission cables, it’s the time to remove the radiator and the oil cooler. They are held only with clamps and are easy to remove. However the fan needs to be loosened before the radiator can be pulled out. Take care of the sharp fins on the radiator to not cut yourself or to ruin it if you want to reuse the radiator.

Radiator fan M110
Loosen the radiator fan to get more access.

When you think you have removed all the hoses and wires that are connected to the engine, then check again, and then recheck the recheck.

Radiator removed from Mercedes W126 280CE
Radiator and oil cooler removed.

There are many wires around the top of the engine, like grounding wires and other various wires and hard vacuum lines. Before you start removing all the cables and vacuum lines, and there is a lot of them, use a camera or write down which one goes where in order for you to remember, then the reassembly will be much less frustrating! You can for instance write on a piece of tape what the wire is connected to and tape it around the wire. Make sure all the wires and vacuum lines that are connected to the chassis are disconnected before removing the engine, otherwise they will be ripped out and broken easily. I will not show all the images of every wire  here, but will show some example pictures.

Various electrical wires
Fuel hard lines
Hidden vacuum lines
Coil and ignition wires

When you think you have removed all the hoses and wires that are connected to the engine, then check again, and then recheck the recheck. It might be a good idea to have an extra pair of eyes. Do not rush it.

Ok, so are you ready to remove the engine? No!! You have to unbolt the engine mounts to free the engine from the chassis first! Do not worry, the engine will not move or fall off while you do this. I do not have the picture here, but you need to unbolt from the underside of the car. There are one hex bolt on each side up inside some holes, use a torch to see them, and an extender for your hexagon bits. The are sitting there quite hard, so make sure you have the hex tool fully inside the bolt before applying force. If you round off these bolts you will have a huge problem! Once they both are removed, the engine is free from it’s base. Lower the car unto the floor again down from the jack stands.

Now and the engine can be pulled out. Move the front bonnet in the vertical upright position, in that way there is no need to remove the hood of the car. The bonnet mechanism is an ingenious design by Benz.

Move your elephant jack in position and use shackles to fasten the engine to the chain, the chain thick enough to withstand at least 300 kg. There are two “ears” which you can fasten to the engine at the rear, and one “ear” at the front of the engine. Take care to not damage any of the injector hard lines that are very close at the right side of the engine, if needed bend them a little to make more room for the shackles. The best would be to use an engine tilter to secure the chains in, but I didn’t have this tool, but it went fine without it, then you just more rely on a helping hand. Since I did not have the engine tilter, I adjusted the chain to be shorter at the front than at the rear ones, so the engine will tilt upwards at the front, in order to get the front part of the engine above the front chassis, and also lower the transmission under the firewall.

M110 engine removal w126
Engine shackled up! Ready to go!

Slowly start lifting the engine with the jack, also making sure the transmission do not hit the ground or it gets stuck at the underside of the car. Make sure all wires are out of the way and they don’t get caught on something. Basically continue until the engine is high enough so it clears the front chassis frame, you might also need to shift the car a little back and forth by pushing it, obviously having the park brake off since you need to move the car often.

M110 Engine removal w126
Engine in mid air, slightly dangerous and time should not be wasted at this point.

Never ever move the engine lifter while the engine is hanging high up. Just push the car backwards when the engine is high enough and immediately lower the engine so it sits just inches above the ground. Then you can start moving the engine it a bit around, but put it down somewhere safe as fast as possible.

M110 engine removed w126
Engine completely removed.

I hope you liked the procedure, now go out and actually do it, cheers!

Cheers, Robs out!

M110 engine mercedes benmz

 Back ground story of this engine pull out

Over the summer back in 2015 I had one goal with dealing with cars and that was to pull a M110 engine and transmission out of the rusty 280SE that had been standing still and taking up space for some years already. The car was destined to be scrapped due to rust, but the condition of the engine and transmission is surprisingly good after over 300.000 kilometers. So I got to it and pulled the engine with the transmission out and then the rest of the car got scrapped. Good riddance, it’s a huge car taking up space for nothing.

How to get a (Gasoline) car starting that has been sitting a few years

As an example I will use this rotten 280SE that has not been driven for a long time. It has been standing outside, somewhat half of it under a roof next to a barn for 3 years.  So how do you solve the mystery of starting a car that has been sitting for so long? This method applies for all Mercedes and all other gasoline cars in general.

280SE M110 Engine
Sleeping M110

I will also touch upon the subject of what you have to do after you get the car started in order to make it drivable.


This list is the bare minimum preparations to get the car starting. To get it to a drivable condition you will need to do much more stuff. I dive into that at the bottom.

  1. Get a new battery
  2. Get some fresh fuel
  3. Get some new spark plugs
  4. New fuel filter and fuel tank filter
  5. Check condition of ignition system to determine if you need to get new parts like distributor cap and spark plug wires.
  6. New air filter
  1. Remove old battery. The old battery is quickly dead if not been used for a while. Just throw out the old one at the same place where you buy new one, they will recycle it for you. Don’t cry over the old battery, maybe this time you will take better care of the newer one?

    old car battery
    Ready to be recycled
  2. Empty the tank from the old fuel since this fuel is pretty much useless. If the car has been sitting for more than a few years then just change the fuel filter as well. There might be the case where you cant raise the car to get under it to drain the fuel and change the fuel tank filter as was the case with this particucular case. Then you have to drain the tank by sucking out the old fuel from the tank filler hole. It is easily done by “stealing fuel trick” (just suck on a hose hopefully not with your mouth, just use a vacuum pump instead). It wont get your filter clean, but often it is not completely clogged in a gasoline car and you can get the car running by pouring some new fuel in.

    removing old fuel
    Removing old fuel from the tank, used the old suck on the hose until it start flowing.
  3. Remove the old spark plugs, they probably are so dirty they won’t give a proper spark.

    old vs new sparkplugs
    Can you spot the which ones are the new spark plugs?
  4. Pour a little oil into the cylinders from an oil can to make better compression upon startup, the oil will make a temporary seal between the compression rings.

    oil being poured into cylinders
    Pour some oil into those cylinders
  5. Put in new the spark plugs, gapped to the right specification.
    spark plug fitting
    Torque the new spark plugs to not damage the engine block threads

    Go over the ignition system again if you didn’t get new parts, like removing obvious corrosion inside the distributor cap. Check for cracks and corrosion on the spark plug wires. Remove all traces of corrosion since it might hinder current to the spark plugs.

  6. Check the engine oil level, fill up if low. Low level might indicate oil leakage and dried up gaskets.
  7. Check radiator coolant level, this has probably evaporated quite a bit and you have to fill up with new coolant.
  8. Throw out the old air filter. Simply remove the air filter housing at initial start up to get the maximum amount of air into the combustion chamber. Don’t forget to put in the new air filter after startup to avoid dirt getting into the engine.
  9. Crank the engine first by hand from the crank pulley, go in clockwise direction when looking from the front of the car over the engine. The engine should be able to turn without too much force. If not you might have a big problem! Then the only chance you have is that the engine will turn with the starter motor.
  10. Check for blown fuses, easy fix and often overlooked.
  11. Put in the new battery and check that the battery pole clamps are cleaned from corrosion. Put them on tight.
  12. Fill the car up with some new fuel, but just a little since you don’t want to waste fuel id you can’t get it started.
  13. Cross your fingers and try to start the car. You know that a good Mercedes should always start unless….

Hopefully you got your car starting, congratulations and pat on the shoulder! Then now what?

rusty 280SE
I managed to get the car starting, and moved it inside, but it is so rusty that it is not worth saving. I will take the engine though since it is in quite good condition from looking at the service history.
After procedure

Some even have the trouble of even moving the car after starting it, can the wheels turn or are the brakes completely seized?

Well the job is not done just because you only got started. Now the big job is starting. The absolute most important thing is changing all the fluids and filters! The fluids change property when being stored for a long time and does not have the right cooling and lubricating properties anymore. That means changing the engine oil, coolant, transmission oil, servo oil, brake fluid and differential fluid.

The brake disks are probably rusted beyond recognition and has to be replaced along with the brake pads and pad sensors.

rusted brake disks
This is a no go

Engine valves needs adjusting if this is not done automatically if you want peak power and better fuel economy.

Serpentine belts needs replacement since they probably are slipping and are cracked.

Change the tires, they probably have cracks in them and are not round at all after sitting this long.

Check the brushes on the generator, they probably need replacing.

Consider cleaning or replacing the injectors since they probably have bad spray patterns making poorer performance and again lower fuel economy.

There is an environmental problem, but only seen in the eyes of us now, in a larger picture this is not new or the worst, 20000 years ago when there was mass extinction of all large mammals on Earth due to over hunting.
Bosch CIS injector
After thoughts

Getting the car started is just a small part of the job, making it drivable is a much more tedious job that might take you . Leaving a car sitting for long periods of time is not good for the car or you. It leaves you a lot of work and more things than you think needs replacement after just a few years. The engine does not like it and it is quite tedious to get rid of all the old fuel in the tank and filters that makes life miserable. Not even to begin mentioning old dried up gaskets.

I have my car parked for around 5 months of the year during the winter, and I do not recommend leaving the car for much more than that. I make sure I do the necessary preparations before parking, like removing the battery to inside a warm place and recharging it before use again. Trying to have as little fuel as possible in the tank when parking. Blowing up the tires to around maximum pressure. Parking the car without touching the brakes and not using the parking brake to prevent seizure. Then covering the car in a car blanket to protect the paint. The brake rotors will unavoidably get a thin rust layer, but thin enough it will all go away rapidly after a going hard on the brakes a few times. Leaving the car for more than one + year will make the rotors so rusty that they have to be replaced. You have been warned.


How to overhaul injectors on older Mercedes Diesel engine

Wow that was a long title! And this topic is even longer. However it is the considered ed as the most effective way to improve performance and fuel economy. There is no point of doing this job unless you did the valve adjustment prior (check out How to Adjust the Valves on a Diesel 617-engine).

When the injectors are getting old, the spray pattern will not be optimal and it will also release pressure at the wrong pressure. This impairs performance and fuel economy. In the long run the time and investment overhauling the injectors will quickly surpass fuel expenses and frustration over poor performance. I got my OM617 engine down to using only 6.5L/100km after replacing the nozzles to a new Monark type and overhauling the injectors. That’s absolutely incredible for a 3.0L diesel engine with technology dating back from the 70s. I also got a noticeably better performance, especially on the higher gears going uphill and during acceleration.

The funny thing about these diesels engines is that they can run even if they have worn out injectors, wrong pressure release, bad timing, tight valves etc. So you will have a poor fuel economy and poor performance, but the car will still run. This can be a good and a bad thing. It will not leave you stranded since the car is still working, but it might lead you to think the engine is just getting old and beyond repair. Even people that have had these cars for 15+ years don’t really notice the gradually decline of power, but sure they must notice the mileage and decide to buy a new car. For us enthusiasts out there, this is the most performance enhancing job you can do to your car.


Quite some preparation is needed, most notably is the need to acquire special tools along with new parts. Don’t be alarmed though, it is not too expensive and you will make the profit back in saved fuel quite fast.

Of the special tools needed for the job, the most significant for testing the release pressure and spray pattern, is the fuel injector pressure tester, this tool is so awesome so it can even be used on Mercedes gasoline injectors. Other tools needed are a torque wrench, a big socket, steel brushes, brass brushes, brass pick tools for cleaning old nozzles, a small pick, a good digital dial caliper for measuring ultra thin shim sizes, also a wise with aluminium protective covers and fine grit sandpaper (1000,2000). You will also need some very clean extra Diesel, half a liter should be enough.

I will by far recommend the pressure tester from, they have specially developed this tool for us DIYs and they also provide all the other tools and parts for overhauling injectors. They even have the Monark nozzles which are better than the Bosch ones. You should also read their guide on the matter which I consider more detailed, however I think more references are always good and you should keep reading to gain more confidence.

The parts needed for doing this kind of job are:

  • A set of new injector nozzles if plan on just replacing the nozzles instead of trying to cleaning the old ones (I recommend to upgrade to Monark nozzles from the old Bosch ones for better performance)
  • A collection of adjusting shims of various sizes (these are super thin shims that adjusts the release pressure in the injector)
  • New crushable gaskets/heat shields for each of the injectors, these have to be replaced every time the injectors are taken out of the engine.
  • New return hoses and the little return end plug on the last injector.
  • New fuel filter and pre filter.
Injector tools and parts for diesel
Injector tools and parts for overhauling the injectors. Most notably is the pressure tester. You will also need a shim set for adjusting and brass cleaning tools.

Before changing the nozzles, a fuel system purge should be done. Use special diesel engine fuel cleaner by disconnecting the fuel line to the tank and running the engine straight from a little container with the fuel return line pouring it in to this container. Run the engine until the diesel cleaner is used up. Change both the diesel filter and the prefilter.

Injector overhaul can be done in one day, but I used two days for avoiding the stress and did things very thorough. I removed and cleaned the glow plug tips and reamed the glow plug holes too, since the injector lines had to be removed anyway and gives access to the glow plugs.


Start by pulling off the return fuel braided hoses, be sure to have some new spare ones on hand.

fuel return lines om617
Remove the old diesel return lines, always replace with new ones to prevent leaks!

Then you have to take off all of the injector hard lines, use a 17mm spanner. Remember that the fuel system has to bled from air every time you open the hard lines on a Diesel, this is different from gasoline engines. This also applies to changing the fuel filter which I think is annoying.

diesel hard lines OM617
Remove the Diesel hard lines

After the Hard lines are removed, you have access to the glow plugs. They don’t have to be removed, but I recommend taking them out for inspection and cleaning the glow plug hole for excess carbon with a reamer. If you are planning to take out the prechamber too, the glow plugs must always be removed or you will damage the engine!

glow plugs OM617
Take out glow plugs for inspection and cleaning

Careful not to loose the little nut and washer on the glow plug cable, you will never find them again down in the engine bay.

Inspect the glow plugs, if you have no record of how old they are, you should replace them safer than sorry.

dirty glow plug OM617
Dirty glow plug full of carbon
Clean glow plug OM617
Glow plug cleaned







Now it is time for using those muscles with a big socket and a long bar for cracking those injector loose, they may sit a bit hard if it’s been long since they were maintained. Remember to crank them open in the right direction.

Engine without injector hard lines
Fuel hard lines removed from injectors

Use an deep over sized socket which can fit over the return hose nipples without damaging them and the socket is still tight enough to fit snugly over the lower fitting. Before taking them out you have to organize a system so you know which injector fits for which cylinder, please do not confuse them with each other. I used a box where I marked each injector with a note. Also ow is the time to take car of the nozzle tips, do not ever bang them into metal otherwise they will be permanently destroyed.

injector removal OM617
Remove injector with the deep socket and long breaker bar

There are crushable washers down in the injector hole. They have to be taken out with a small pick and thrown away since they cannot be reused.

crushable washer under injector OM617
Remove the crushable washers with a pick. Note the direction of the washer!

When all the injectors are out and you hopefully remember or organized which ones went where, it is time for pressure testing the injectors BEFORE you start overhauling them. Why? Because you will know the condition of the nozzles and what kind of performance increase you can be expecting. Also it is used to predict the adjustment when you assemble the injectors. Even if I had in mind to just replace the nozzles I was still curious to look at the spray pattern and pressure reading for getting an idea of the condition of the injectors. This car had Bosch nozzles and the pressure readings was around 1500PSI (which is not too bad though the pressure should be around 1700PSI when optimal), and even the spray pattern was in a decent state. The injectors  was in a better state than I feared and the old nozzles was more than usable, but I still decided to change for new Monark nozzles for better performance and prevent me for doing this same job in some years. I can then have the old Bosch ones as backup nozzles with good confidence for the future, of course after cleaning them.

Do a pressure test, note down spray pattern and pressure release for each injector before dismantling, the spray should be a fine mist making a fan shaped pattern. Be sure to wear a gas mask like the ones used for paints to prevent inhaling harmful Diesel fumes, this is very important! Also place the injector inside a clear bottle to prevent fumes spraying all over. Lastly do this job outside in order to not be breathing Diesel the entire following week!

The pressure is built up steadily with a slow pump on the tester, when the injectors squirts, do some repetitive pushes to note the release pressure.

pressure testing setup
Ready for pressure testing, not that you should use a clear bottle with the injector inside it when doing the actual testing to prevent harmful fumes.

After testing each injector, you can open them/ separate the injectors in a wise with aluminium protection grips by placing the flat upper half down into the wise while using the same socket over the lower half. Use the out most care to not touch the nozzle tip with any metal. Muscles are usually needed to open them the first time due to corrotion.

opening the injector for mercedes Diesel
Separating the injector halves with use of a wise with aluminium grips

When you cracked it open, be sure to open it over a box to catch all the components coming out.


Now over to the fun part, cleaning the injector parts! This is by far the most time consuming part. You need to use quite a lot of time on each injector at a time and be sure to not mess up the internal parts with each other, since they will be near impossible to adjust and might leak fuel.

The easiest way is actually to cook each injector in a kettle with soapy water for some minutes, before cleaning each part with steel and brass brushes. The sediments will come much easier off then.

cooking injector parts
Cooking car parts in the kitchen, typical weekend meal.

After cooking and not eating, the hard labour of cleaning the small injector parts can begin.

cooked injector parts
Cooked injector parts, careful when hot. Note I have marked the injector number so I can keep track.

Use only brass brushes on the inside parts to avoid scoring the metal! On the outside of the injector housing you can use a steel brush. Use small brass picks to clean the crud out of the internal hard to get corners and inside the injector housing.

Cleaning inside injector parts with brass brush
Cleaning inside injector parts with brass brush

When you have cleaned all the parts, and not messing up the parts with other injectors, the adjusting can begin. This is the most fun part.

It is very important to do a thing called lapping before assembling the injector parts after cleaning. It involves flattening the internal pieces that goes together in the joint between the injector halves on very fine sandpaper on flat a piece of glass to make the surfaces exceptionally super flat. As you might have noticed the injectors do not have internal rubber gaskets and the super flat metal surfaces in contact with each other makes the seal between the injector halves.

lapping the injector halve pieces
Lapping on a flat piece of glass and fine grit sandpaper, you will need to polish this part and the lower edge of the upper injector housing.

Start by using the 1000 grit paper if you have some bigger scratches, then switch over to the 2000 grit to get the perfect polish. I only used 2000 grit on my parts.

Adjustment shims for injectors
Selection of adjustment shims

Use the notes from the initial pressure readings to “predict” the new pressure readings. The adjustment is done by adding or removing adjustment shims to obtain the right pressure. The pressure increases with approximately 100PSI with adding 0.05mm shims and decreases by the same 100PSI by reducing the thickness by 0.05mm. It may take some tries to get the wanted pressure settings. I aimed for 1800PSI on my non turbo engine, The factory manual says 1668-1780PSI, but you can safely go 50PSI over because the new nozzles will wear and the pressure will go down. Several shims can be added on top of each other for obtaining the right overall thickness.

Dial Caliper to measure shim sizes
Use the Dial Caliper to measure shim sizes

Adjustment Example:

Initial test: 1500PSI
Original shim: 1.45mm
Aimed pressure: 1800PSI
Adjustment shims extra required: 1 x 0.10mm + 1 x 0.05mm ~ +300psi

Note that having similar release pressures between all five(or four) the injectors within a maximum difference of 50PSI are more important than trying to aim single injectors to be dead on 1780PSI for example. This is to ensure smooth engine operation and reduced vibration and noise. If All your injectors are within 1750 and 1800PSI the result will be satisfactory. Some injectors are almost impossible to get the exact value you want due to age and spring wear. I didn’t have problems with getting them quite accurate at around 1800PSI so it’s not impossible.

Also now it the time for replacing new nozzles if you plan to do so. Be ultra careful of the new nozzle tips by  not smashing them into other metal.

Old Bosch nozzle tips
Old Bosch nozzle tips, note the little hole on the tip.
New Monark nozzle tips
New Monark nozzle tips. Note that the Monark nozzles does not have the little hole in the tip

Assemble the injectors the right way with using your selected adjuster shims. This part is iterative, since you have to assemble the injector, tighten the halves with a torque spanner, test for leaks and spray release pattern. Make notes as you do the testing, and open up and adjust the shim sizes if necessary, you may need to do this several time to get the pressure right.

Be very careful not to touch the nozzle tip during assembly and disassembly, take good time and care. Especially the Monark nozzle tip is quite pointy and you should take care to not even touch it with your finger.

Cleaned injector
Cleaned injector, as good as new

When every injector is tested, adjusted, checked for leaks and balanced between each other, they are ready to be placed back into the car.

fuel injectors OM617
Cleaned fuel injectors, adjusted and with new Monark nozzles.

Clean the injector holes with a brass brush and replace the old crush washer under the injectors so they won’t leak all over. Tighten them down to 75- 80Nm.

Cleaning fuel injector hole with brass brush
Cleaning fuel injector hole with brass brush

Clean the glow plug holes for excess carbon build up with a reamer and reinsert the glow plugs and connect the glow plug wires. Too much carbon in the glow plug hole might lead to shorting of the glow plugs, making cold starts nearly impossible.

Cleaning excess carbon with reamer
Cleaning excess carbon with a glow plug hole reamer

Attach all the fittings and injector lines and new braided rubber return lines as well as the end plug on the fifth injector. Do not fully tighten the hard line fittings at the injector end.

Now the air has to be bled out of the fuel system. Start by pumping the air bleeder pump at the fuel pump until fuel comes out of the hard line end. Now you should get a helper to observe if fuel are coming out while you are cranking the engine. The bleeding has to be done while cranking the engine while flooring the accelerator pedal, again make sure the hard lines are not fully tightened, leave 2/3s of a turn. When fuel starts leaking out of the lines, stop the cranking, tighten the nuts and start the engine normally. It might cough and run rough until all air in the system is gone. This is especially the case if you have a bad bleeder pump. Check for leaks while the engine is running and then take a test drive until engine is warm, recheck for leaks and do necessary work if leaks are evident. If diesel is coming out from the halves of the injector, then it must be lapped again. If fuel is leaking from the bottom of the injector, it is probably the prechamber seal, this is a bigger job to get out, but leaking fuel is expensive and should be dealt with.

Happy injectors, delivering more power for less money. Cheers!


How to do a coolant change on the M110 engine

Changing the coolant should be done every two years or so, to keep sediment buildup inside the radiator and engine block. It is one of the most easy things you can do and waste of money paying a workshop for doing it.

Depending on the climate you are in, the amount of antifreeze in the coolant needs to be determined. The amount of coolant in the M110 engine is in total 10 liters. Since I have the car in Norway I use a 50/50 mix water and antifreeze, so I needed to buy 5 liters of antifreeze and mix this with water. The antifreeze also contains anti corrosive properties, so I recommend not to use pure water even if the temperature is always above freezing.


Put your heaters on maximum, this will allow for maximum flow of coolant.

heater controls
Put the heaters on maximum.

Jack up the front of the car and put it on jack stands. Have a bucket or similar for collecting the old coolant, place it under the radiator. Open the radiator coolant cap, only if engine is not super hot. Then remove the radiator drain plug, be careful if the engine is hot and you might burn yourself on the coolant.

radiator drain plug
Remove radiator drain plug

Let the coolant flow until it stops. Now you might think that’s it, but no! There are lots of more coolant left in the engine block, so you have to remove the coolant plug from there as well, this is the reason you had to jack up the car in the first place.

The engine block coolant drain plug is located on the right side of the engine just beside the engine mounts. It’s quite big and the only one there so you will find it in no time.

engine block coolant drain plug
Locate and remove the engine coolant drain plug.

Let it drain, then reinstall both plugs. Now is a good time to check those coolant hoses, if they fail it might result in complete engine failure. Especially inspect the top and bottom hoses from your radiator, take a grab of them and see if they are loose. Also squeeze and see if they have cracks. Replace immediately if you see any cracks. A hose is quite much cheaper than a new engine.

Now pour in your 10 liters of coolant until the maximum mark through the radiator cap. If you over fill the radiator will just spit out the top. It is important to start the engine without the radiator cap for venting the coolant system of air. Air will make your engine too hot. Let it run for a couple of minutes and then check the level and refill some more if needed. When your engine have stopped burping, there should be no air left in the coolant system. Check for leaks, then you are done.


Bonus tip:

If your thermostat is old, then it is a good time for replacing it while doing the coolant change. However getting the thermostat housing open can be tricky, I have encountered bolts that have frozen in the aluminium housing so I had to drill them out. Be patient and use lots of wd-40. Wiggle the bolt by trying too loosen it, then tighten it slightly while hammering on it, maybe even use heat. If you change thermostats every 5 years this should be no problem though. After 25 years the bolts are probably stuck.