Thinking of w123 – Reputation of a classic

Reading Time: 4 minutes

Currently we think of the Mercedes-Benz w123 as the perfect Mercedes model which is pretty much a flawless classic. It is a car that resides in the super league of renown young classic cars. It is true they outlasted most other cars from that era and have a reputation for “superior” build quality and “reliability”. The w123 has indeed a large place in many people’s heart and often bring about memories and stories when nice examples roll by on the street. However the cult status of the w123 has maybe become a little skewered and starting negative discussions of the model is frowned upon in quite ideological ways. In hindsight this classic’s reputation might have become a little biased, as with most renowned classics (read: Ferrari).

Don’t worry I’m not trying to discredit the w123, but trying to convey a more realistic perspective of the model as a car looking away from the icon status. As any car or man-made object, the w123 is not perfect and comes with its quarks and weird engineering.

I was looking through an old review from 1977 of the 280E in Motor Sport Magazine written when the w123 was brand new. This is the perfect time to look into an unbiased opinion for the times and comparison to other cars at the market. If you want to read the full article, it can be found at https://www.motorsportmagazine.com/archive/article/march-1977/37/mercedes-280e-w123

I’ll give some of the highlights opinion from the review under with my own comments on the matter:

Complaints

Complaint 1: One complaint is that the car is too expensive for the time, you could get more luxury and more performance in a Jaguar for less money. Also the extra equipment is expensive and 280 base model without electrical windows or sunroof starts at £8495 which is roughly £52700 in today’s money. Quite a lot!
Comment: This makes sense in 1977, but as time has shown, the Jaguar had many issues especially with QC and the electrical system. Mercedes is a better built car overall, but is not as sporty with smaller (more boring?) engines and less equipment in general. In hindsight when you look at how long many of these cars have lasted, maybe it was not so expensive after all?

Complaint 2: Another complaint in the article is the low power of the 280 engine (remember this early version had only 177hp compared tot he 186hp of later models) and the author misses a bit the V8 power for this top w123 model which only clocks in 0-100km/h in 10s. The kick down is pointed out to be bit slow and the author recommends to keep in S when overtaking. Fuel efficiency was also not the best at its time where the author also points out that the engine is quite thirsty with 16-18mpg (12-14 L/100km).
Comment: I quite can understand the lack of performance when compared to cheaper Jaguars and BMWs at the time, but Mercedes never wanted this to be a sports car. That was reserved to the SL and top of the line S-class. The upgrades to the M110 engine in 1981 did increased its power and probably lowered fuel consumption a bit. I run mine 280CE from 1984 usually around 10 L/100km. The kick down is indeed a bit slow to react, much faster to manually stick in S with the auto transmission.

Complaint 3: Plain interior and cheap plastic is used. The author points out the spartan interior, sparse use of real wood and really nasty cheap plastic used for the side door pockets. Also the boot has a cheap looking tool kit compared to a BMW.
Comment: The interior is very plain, but has kept the styling somehow timeless and looks nice too this day. I personally really enjoy the large air vents int the dash. The cheap looking plastic used on the doors rarely breaks. This is another story for the notorious glove compartment-lid. It always breaks and is definitely cheap plastic. The author credits the seats for being quite firm and good, but I think the seat comfort can be quite uncomfortable on long rides. I wonder how other cars were at this time?

Complaint 4: Road and engine noise. The complaint is that Jaguars are superior in this department. Especially the wind noise from the large and flat non-aerodynamic mirrors. Poor engine noise insulation is pointed out too.
Comment: Agreed, quite some wind noise especially in the coupe version. The wheel sills can clearly be heard on gravel roads. Also the engine valve tick is clearly audible in to the passenger compartment. They should have put a bit more sound proofing, but it does save weight in the end.

Recognition

Recognition 1: Rev happy engine. The straight six is very rev happy going up to 6500 before the red-line. The author also points out the engine has superior smoothness to V8s at the time.
Comment: A bit contradiction to the first complaint, but I see the point since you need to get the revs up since it lacks the low end power of a V8. I think the M110 feels fast and can keep up with modern traffic pain free. The straight inline 6s have perfect balance and are superior to any other engine configuration. It’s one among the economic reasons why Mercedes has reintroduced them in their new cars and is planning to discontinue V6 production.

Recognition 2: Brilliant suspension and road handling. The w123 utilizes the latest technology from the S-class at a cheaper standpoint. There is little body roll and the ride feels more comfortable than harsh BMWs while still being agile. Also the car has wet weather stability than the S-class. Super maneuverability with the recirculating-ball servo. Also impeccable braking with large disk breaks on all four wheels.
Comment: This I totally agree with! You can toss the w123 around mountainous roads at full speed without being daunted, there is a clear indication when you are pushing the limit with the classic wheel whine without the car going sideways. There is a reason why there were so many w123 Taxis going around back then, they can easily turn on a dime in the city. I was not aware that the ride was better than the S-class (w116) in wet. KUDOS!
NOTE: I should point out that you can get two different dampers to w123: Comfort and Firm. I will highly recommend the latter due to less body roll. I also recommend to go for the Bilstein dampers!

Recognition 3: Business as usual with effortless automatic door locks, boot and filler cap. Simple control of the functions such as lights, wipers and mirror adjustment. No fuzz about. The headlights can be adjusted with a single knob.
Comment: This makes Mercedes so easy to operate so you can focus on the driving without getting lost trying to find the door knobs. It makes the car a bit spartan and have a modern compared to other classic cars. Many do indeed enjoying the weird features and quarks of old Porsche and Italian classics.

There is much more details in the magazine. I hope this gives some more nuances of a classic car such as the w123. Happy reading.

Cheers, Robs out!

How to adjust the valves in the M110 engine – Part 1.5

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.

Reading Time: 3 minutes

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!

Mercedes late 70s DOHC valve spring compressor tool.
Mercedes late 70s DOHC Valve spring compressor tool for several engine models.
M110 DOHC valve compressor tool
This is the M110 engine specific tool which is out of production. Looks similar right? Although not the same, I’m sure we can adjust the obtained one to do the same job with some modifications.

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.

Valve spring compressors
It came with 4 different valve compressors. I might use the second from the left with some modifications.

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 tried to overlay this tool over the valve and camshaft arrangement in the M110 engine. Here The sizes are not 1:1 but illustrates the point. Already here we can see that there might be clearance issues between the engine wall and the compressor. Also the circular edge for the compressor surface has to be cut, so it can slide onto the valve top under 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.

AC Part 4: Changing the Expansion valve in w123

Reading Time: 3 minutes

Changing the AC expansion valve

An old and defect expansion valve will decrease performance in your AC system. That can result in either the commonly too warm air, or in fact too cold air causing frost on the vents! The air can also alternate between these two modes. The more expensive consequence is that it can also wreak havoc on the AC compressor since coolant will always flow (unless the compressor has a shut-off clutch).

In the final part of this “AC 101” series we will look at changing the expansion valve. If you need to read upon how the expansion valve works in an AC system look at Air Condition Systems 101.

The Ac expansion valve is quite accessible under the passenger side dashboard, but you will need some large spanners to loosen the AC hoses.

Preparation 

Before you do anything, make sure the AC system is completely emptied of refrigerant at a workshop. I repeat what I have written earlier in this series; The AC refrigerant is a highly volatile greenhouse gas. And if you have an old R12 system, the system might contain old freon gas which will deplete the ozone layer as well as being a volatile greenhouse gas.

So do that and then go shopping.

Parts:
  • New Expansion valve
  • New AC gaskets – You should change these to avoid leaks.
Tools:
  • Philips Screwdriver
  • Little flat screwdriver
  • Large open ended spanners

Procedure

Removal

Start by removing the passenger side lower dashboard cover. It is held in place with three screws at the top under some brittle plastic covers and a plastic screw on the lower right hand side. Remember when dealing with old interiors you have to take extreme care to not breaking any parts or loosing them. Replacement parts are long out of production by now and are not available except used ones (if you can find them) at often very high prices.

Passenger side dashboard ccover MB W123

Use a narrow and thin flat head screwdriver to carefully pry off the three small plastic covers.

Removing lower passenger dashboard cover MB w123

Then  unscrew the three philips screws on top and the lower right plastic screw. The left side and back side of the dash cover is held up by tabs in the floor and wall construction.

Removing lower dashboard cover w123
Weird plastic screw location

With the cover off. You can immediately locate the AC expansion valve. You should detach one end of the ventilation hose so you can access it. Detaching it from the left side is much easier and you don’t end up breaking stuff.

AC expansion valve w123
The Expansion Valve was covered in some very old foam that is disintegrating.

The expansion valve is covered by some foam that is long past its lifespan. Touch it and it disintegrates. So be prepared to get some styrofoam replacement (which you have to fabricate yourself). The only practical function of this foam is to protect the other plastic from the very cold valve.

Start by unscrewing the hoses, they might site quite hard and getting to them is a bit of a grind. Start by removing those who you find easiest and remove the other ones as you go.

AC expansion valve w123

Note the orientation of the old valve before removing.

AC expansion valve removed w123
AC expansion valve is removed

After the expansion valve is removed you should change the old gaskets with new ones before you install the new expansion valve.

The new expansion valve also says R134 on the side so it can in fact work fine with newer AC systems. The old one was for the obsolete R12 system.

AC Expansion valves Mercedes w123
New vs old AC Expansion valve

Installation

Remember to change the  gaskets and then start to screw in the hoses making really sure not to cross thread them. Take your time here. The hoses should go on quite tight to make a tight seal under the pressurized gas.

AC Expansion valve R134 w123
New expansion valve installed. It says R134 on it so it will work better with the R134 systems since R12 is obsolete. Notice the styrofoam placed on the backside.

Then install the dashboard cover again and your job is done, for now at least.

I highly recommend to perform pressure testing of the AC system before filling it with new gas, since many workshops do not even do this before they fill. You basically have to demand it before they fill. An AC leak is quite nasty since you will get a dirty cleanup job, not mentioning the greenhouse gas effects…

Cheers, Robs out!

How to do a fuel filter change on w123 – Petrol engine

Reading Time: 3 minutes

How to change the Fuel filter

So how do you change the fuel filter? It is in theory simple, but in practice it can be quite messy and also tricky to fully access in the rear end fuel delivery system on the w123 chassis. You also need to make sure you have as low fuel as possible or drain the fuel tank dry.

WARNING :
There is a high explosion and fire risk when dealing with petrol fumes, so don’t light up your cigarette and avoid sparks!

Preparation 

Make sure you inspect the fuel delivery system, since a lot of parts there might need to be changed along with the fuel filter, and since you are already draining fuel you don’t want to do this again in 2 months. See the older article on How to re-haul the rear fuel delivery system on w123 (gasoline)

Part requirements:

  • New Fuel filter
  • Optional parts:
    • Fuel delivery assembly rubber bushings – I highly recommend to change these
    • Fuel pump
    • Fuel accumulator
    • Fuel hoses
      • Main tank hose
      • High pressure hose
      • Low pressure hoses
    • Fuel hard line and fittings

Tools:

  • Spanners
  • Sockets
  • Hose clamp

Procedure 

You need to access the rear end fuel delivery system on the rear right end of the car. It consists of the fuel pump, fuel filter and the fuel accumulator. They are suspended from 4 rubber bushings secured in a weird metal clamp. It is partly hidden behind a plastic cover near the right rear wheel.

Removal 

Start by removing the battery, trust me, you dont’ want sparks while working under the car with petrol fumes! And don’t smoke!

Then jack up the rear end of the car up on jack stands and block the front wheels from rolling. As extra safety measure I always leave the jack in raised position on the same side as I will be working.

Remove the rear right wheel and you have better access to the fuel delivery system. Locate the plastic cover which is held by a few screws, use a long thin socket extension to remove these.

Fuel delivery assembly w123

Now you have to drain the fuel from the tank to avoid petrol spills and excessive fumes. This can either be done with using a vacuum pump with a  hose down into the filler neck, or by disconnecting the main hose to the fuel pump. It will also leak fuel from the delivery line to the engine, and this can be blocked from continuously dripping with a hose clamp on the high pressure hose. Make sure the clamp is of high quality with no sharp edges, since a new high pressure hose is quite expensive.

Fuel filter removed
Fuel filter removed. Notice the high pressure hose is clamped.

When the fuel is drained. You can start by loosening the 2 lines that connects to the fuel filter. The left side (from rear) is the high pressure line and the right is the hard line. Notice the position of the two copper washers on the hard line fitting.  A lot more fuel will now drain out from the filter so take care. It is possible to remove the filter from the cage without removing the whole assembly.

Rubber bishings fuel pump w123
Installing new rubber bushings for fuel pump assembly.

If you need to also change the rubber bushings, then change them one by one and you don’t have to take the whole assembly down. Alternatively to get better access you can secure the assembly with zip ties while changing them.

Fuel delivery assembly w123
New bushings installed

Installation 

Installation is pretty much reverse of removal, but you have to remember to use the new copper washers that followed with the new filter. Also I found that you need to torque down the screw between the hard line and the filter for it to not leak.

After everything is put together and you have put some fuel in the tank, try to start the car, it should not take long for the engine to fire up after you crank it. The fuel pump is pretty quick pushing fuel through. When the car is running, go back and inspect carefully if fuel is leaking and check for any wetness.

New fuel filter installed on w123
New fuel filter installed.

If it’s dripping or you can see wetness, shut off the car. Tighten the bolts, wipe off the fuel so it’s completely dry and try again. I had to redo this step twice before it was properly sealed, and the leak was indeed between the new copper washers and the hard line. The copper washers will actually start to seal better when exposed to moisture and some small corrosion will start forming in the gaps.

Be sure to check for any wetness under the rear end of your car after you parked it the first times, since leaking fuel is bad for your wallet and is a potential fire hazard.

Cheers, Robs out!