Part 1.5 of valve adjustment of Mercedes M110 Engine. Stuck valve adjusting nuts require a DOHC valve compressor tool, which is hard to obtain for this engine.
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Christmas came early..
Notice the part 1.5 nonsense, what is that all about you might think to yourself? Have I gotten mad over New Year’s? It’s rather just because of the half usefulness of this article. Since you readers are mostly DIY mechanics and Mercedes enthusiasts, I want to convey a story of the journey toward valve adjustments of such an old engine. In this way we share the ups and downs, the challenges and successes, and maybe learn something on the way.
Remember in Part 1 https://mercbenz123.com/posts/valve-adjustment-m110-engine-part1/ where I ended with 4 different options listed with increasing price and pain? Well since Christmas came early (2018) I ended up somewhere with a solution in the middle of option 1 and 2. After trawling the used car tool market, mostly ebay, I managed to find a seller which sold a late 70s vintage Mercedes valve compressor kit for DOHC engines. Although not specific to the M110 engine it is close enough, that with a few modifications it might just work. Let me just say it was the most expensive vintage tool I have ever bought. Lets hope it can come to good use!
I almost did not buy due to the high asking bidding price, but after the deadline was reached it was still for sale. I decided to go for it as a Christmas present for myself and bid on the tool for a little less. Chance happened that we compromised and reached a fast deal. Two weeks before Christmas it landed in the mail box.
It comes with 4 different valve compressors, although I’m not sure if any of them fit right out of the box. I might need to adjust one of them. The lever bar has a simple screw on attachment to swap out the compressor ends. The Hook is not attached, but can be placed in different grooves. I might also need to adjust the arrangement here as well.
Under I have tried to visualize how the tool is operated on the valve head. The idea is to compress the valve just enough so I can slide off the rocker arm. Since the valve clearance adjusting nuts are so tight we need a socket over the nut which is naturally blocked by the rocker arm.
I’m excited to see how the tool can be used in real life, but since it’s winter and the car is hidden away, this have to wait until spring. I’ll keep you posted on the progress in this journey as soon as possible.
Cheers! Robs out
Other news: I tried to sell the S600 in the autumn, but was unfortunately little interest which is hard to believe when regarding the current economics and huge interest in classic cars. Norway is a weird country.. The car is in mint condition with low mileage so I will not give it away for free. I will instead keep it and enjoy it, make some good articles about the w140 and let time mature it into a true classic.
I planned the valve adjustment job to be straightforward and easy, making it a delight to write an article about afterwards, but no! In the end I could not even adjust a single valve out of the 12 in total, and this is why I will divide the so called adventure into multiple parts and share my experience on the topic.
“Mother nature beats father engineer every time..”
Valve adjustments should be done every 15.000 km which means for most people every 2. or 3. year and is important for engine performance and fuel consumption. Neglected maintenance can even end up wearing your cam lobes prematurely if they get too tight!
A story of success
I got all the parts I needed, that is really only a valve cover gasket set. I let the car stay overnight for the engine to cool down. Then I start pulling out the spark plug wires, no need to mark them with cylinder number..haha! I unbolt the valve cover in a breeze, the nuts I throw somewhere neat.
Then I check the valve lobe timing, oh see that the first one is perfectly aligned already so I can start adjusting the first valve immediately. I find my valve feeler gauge easily from the toolbox and it’s not rusted together at all. I adjust the first valve and since my memory is faultless I can easily keep track of all the valves I have adjusted and the ones who are left. The crank is so easy to turn by hand and I don’t need to remove the radiator shroud or anything silly like that. I get everything done in under a less hour and bolt everything together with the new valve valve gasket and I’m now already on my way to the race track with 40 more HP.
This is all however a big lie.
Sometimes wisdom words are painfully true: “Mother nature beats father engineer every time..”. The real struggle you can follow below.
So before starting you should take care of a few things. In theory a valve adjustment is easy and requires little preparation and engine know how. You need a new valve cover replacement kit, since your old one is probably leaking oil and a new one is very cheap. The valve adjustment can be made either when the engine is warm (just after driving) or cold (20°C). I really recommend the latter since you will not burn your fingers and get better results since the engine is not cooling down slowly. Ideally it should be at ambient summer temperatures in the shade. You have to leave the car overnight to properly cool down after driving so this have to be planned in advance.
The tools you need is just really a spanner and some feeler gauges for the adjustment and a socket for turning the crank over, but as we will see here this is not the case for my case.
I start by removing the air filter housing to access the valve cover freely. Then I mark every spark plug wire with a number on a piece of tape. Usually the spark plug wires are different length, but it’s so much easier to plug them in afterwards. Then I take out the spark plugs.
Now I can start removing the valve cover bolts and place them somewhere safe. I note that the middle ones have a copper shim which I can keep, but the new valve cover gasket comes with replacement ones. It’s always nice to keep bolts, nuts and shims if they are in good order.
NOTE OF CAUTION With the valve cover off is is extremely important to not drop anything into the engine like a nut or something, since this will cause catastrophic engine failure. Also keep dirt away and exercise hospital level cleanliness while the engine is open. Cover it always when not working on it, like lunch break etc..
I then go in the the toolbox to find my gauge feeler blades and realize they have rusted together and end up throwing them. I go in my dad’s old toolbox and luckily find some that are in a bit better shape. With a cold engine the inlet valve clearing should be 0.10 mm and the exhaust 0.25 mm. I draw a diagram over the valves so I can mark them after every adjustment, it will be very hard to keep track of otherwise. Just try remembering 12 boolean positions for reference!
Of course none of the valve lobes are pointing directly vertical for any of the valves after opening the cover, that would be too easy! So I go ahead and try to turn the crank, but come over a problem. The fan shroud is too tight to engine for me to get any socket tool and ratchet to the crank. Loosening just the fan shroud is not helping either since the fan is sitting tight to the shroud. Then I loosen the fan and I can just get enough room for the ratchet and finally being able to turn the crank.
I align the first cam lobe and is ready to check the valve clearing. I expect most of the valves to be to bee way too tight, and the first one is as expected. I grab my spanner to start adjusting, but the valve adjusting nut is not moving at all. In fact I’m starting to slightly round off the nut. I stop before I ruin it. Then I quickly check a few other valves, they are all tight as expected, but also here the valve adjusting nuts are super tight. I am totally stuck.
After searching the Internet for similar issues it seems this is a common scenario for these aging engines. The nut material is quite soft and can easily be rounded off when they are tight. The solution is to remove the rocker arms to access the whole nut so you can get a socket over it to exert more force.
Seems easy right? To remove the rocker arm you need to depress the valves somehow. They are under very high pressure from the valve springs and a special compressor tool is needed. There are many different DOHC valve spring compressor tools on the market, however the M110 engine have very tight space between the cams and the engine walls where the spring compressor have to fit. And the valve is at an angle so the tool need to be just for this purpose. There is such a speciality tool for the M110 engine, but I can’t find it on a single place on the internet. It turns out it is in fact out of production. Fuck!
I am stuck and have to abandon my job and put everything back together. This was a waste of time! (But in the back of my cynical mind I think it can be turned into an article at some point..)
Here is a diagram over the valve assembly to illustrate the point better.
The valve compressor tool is like a leverage bar with a hook for the cam axle and a crow foot depressor at an angle that can slide between the engine wall and the cam axle down on the top of the valve. It looks like this:
how to solve the tool problem
I have considered some options below and ranked them from easier/cheaper towards more expensive options.
Obtain the tool
I have reallly tried to find this on the internet, but with no success. I think I will not be able to obtain it. Not sure if Mercedes has one , but I am scared of even asking, it’s probably super expensive.
Make the tool myself
I know how it looks like and roughly the sizes. I can easily obtain some steel, and a crow foot. I have a welder so I can make the tool. However I expect it to take some time to assemble. Definitely worth looking into.
Take the car it to a workshop
I can just take it to a workshop and tell them to adjust the valves, but they are going to run into the same problems like me and they might end up ruining the valve nuts unless I explicitly tell them the problem in great detail. Remember these days no cars require manual valve adjustment and only the more experienced mechanics have done this. If you want things done right, better do it yourself.
Contact Mercedes on how the fuck….
This is my last option and will consist of asking if they have such a tool, and if the tool is not for sale (or out of production), if they can at least adjust the valves if they can send a tool from Mercedes Classic in Germany to their workshop. Problem is that is going to be very expensive for a simple job. Not likely I will venture down this path. Also would turn into a dreadfully boring article for you DIY people!
More on this adventure when we return in Part 2 of the valve adjustment nightmare… soonish
Reading Time: 3minutesThe fuel delivery system on w123 consists the fuel tank and a collection of components until it reaches the combustion chamber. This article will focus on the rear components until it reaches the CIS fuel injector assembly. The CIS system is pretty much a black box for me still. I will however go through how you change the fuel injectors and gaskets in another article.
I had to do a re-haul of the entire rear fuel delivery system when an entire tank worth of gasoline (~80 liters) had leaked out after my 280CE was parked for a while, totally delayed my plans for cruising in the summer by almost a week. This made me furious and is the reason for why I wrote this article.
It is up to you how many part you want to change. I would recommend to change all the rubber fuel hoses and fuel filters as a minimum!
New fuel tank filter (the first one)
New main fuel tank delivery hose
New fuel delivery filter (the second one)
New high pressure flexible fuel hose
Two other fuel hoses and clamps (see pics)
4 fuel assembly rubber mounts
[New fuel accumulator?]
[New electric fuel pump?]
So why bother changing the fuel accumulator? Well it can lead to problems such as warm start problems (yeah the M110 usually have warm start problems more than cold starts), this is due to the inability to hold fuel pressure after shutting down the engine and starting it before it gets cold. There are separate start up procedures either if engine is cold or warm. I thought a broken fuel accumulator was the problem with my car’s warm start problems, but it was in fact the old injectors and brittle gaskets that was the cause since they could not maintain fuel pressure.
Why bother changing the electric fuel pump? This has to be the number one reason why people are stranded in their cars with M110 engine. After some time (around 7 years if in daily use) it will with certainty stop working. The part is however quite expensive and I would suggest to not change it if is still working and not obviously very old. A maintenance tip instead of investing in a new part is to remove the corrosion on the electrical connections.
Pretty straight forward, just change all the fuel hoses and refit… OK I will guide you through it like Gandalf in the mines of Moria. Smelling fuel is usually an indication of leaking hoses.
Before you even start you have to disconnect the battery to avoid explosions. Then completely drain the tank, either by sucking up the fuel from the gas filler tube or by unloosening the main tank outlet hose from under the tank. I would suggest you drive the car nearly empty before undertaking this task. Make sure the area you are working in is very well ventilated since gasoline fume is highly explosive!
After the tank is drained you can remove the plastic cover start by removing the thick fuel hose connected to the tank. Just have a look at this one in the picture under which caused all the fuel in my car to drain out.
A massive 45mm socket is needed to remove and fit the fuel tank filter. Remember to replace the gasket as well.
Now you can remove the flexible hoses connecting the high pressure and the return hard lines. If you see rust on the connection then you have to be extremely careful not to round off the relatively soft metal on the hard line unless you want to go through with replacing the entire line. Believe me this is a shit job (my old hard lines were rusted and leaked fuel).
Disconnect the two electrical wires to the fuel pump and when all the fuel lines are disconnected from the body, you can go on and loosen the 4 bolts holding the bracket for the pump, fuel filter and accumulator. Beware this bracket can be pretty rusted and you need either to get hold of a new one or remove the rust and repaint the one you have. The rubber mount bushings are probably dried up or broken so you should replace all 4 of them.
On a work bench you can now go on with the job of replacing the components and the old fuel hoses. Look at the picture below on comparing new and old hoses.
Assembly is just opposite of removing. The main thing you have to consider is to make sure there are not any leaks before you start driving. Look at the picture below to see how the components should fit together in the assembly.
The best thing is that there is no need of special fuel bleeding or start up procedure when starting up the car after fitting all the lines together. Just refill the tank and crank the engine and it will start right up. Nothing difficult as with the diesel.
Then mount the assembly and fasten the hose to the fuel filter. Don’t forget to fit the electrical wires to the fuel pump and mount check for leaks when starting the car. When no leaks are detected, mount back the plastic mud cover to protect the components. Hopefully you will have no leaky days or being stranded by a malfunctioning fuel pump.
The car is welded, put together again and finished! Who would believe that? I am super proud of my own work. I managed to strip downm weld and then assemble the car on a tight schedule. In the process I learned how to weld body panels. I in fact learned so much through this project that I know tons of new stuff about W123s. This job was the inspiration to create this very site.
The project included the tricky disassembly of the whole rear sub frame and drive train with following refurbish. This has been almost two years of work, although with large gaps between quite intensive working periods.
Which areas did I end up welding? I couldn’t cover all of them in the blog.
Front and left wall in the front seat foot area, the part that let water into the floor.
Sounds like a lot, the issue was that it had many places with small holes, and with welding the job is just as long when it involves small or large areas. You still have to remove old metal, remove paint and body protector coating, maybe interior parts, cut out new metal piece and shape it, weld it in place, grind it, polish it and paint it. Same process over and over again.
What mechanical areas did I fix? The car was from before very mechanical sound and basically I just replaced rubber wearing parts.
New flex disks for drive-shaft
New center bearing and hanger for drive-shaft
New upper control arms and sway bar bushings at the front suspension
New shock absorbers, Bilstein original extra stiff for flatter cornering
New fuel hard lines and rubber hoses
New sway bar bushings and links rear
New subframe rubber mounts
New brake rotors and pads
Basically all the lower sides and front needs repaint, these are areas not so visible, none the less I got some paint with the right color code (172).
So what is the result? Well a car that looks really good and drives like like a new Mercedes. Super smooth and fast!