300SE stumble at idle

The 300SE had a severe stumble at idle.   It only occurred when the engine was hot.  It never stalled the engine, but felt like it was about to.    There was also a miss at takeoff.    My initial thought was to check the distributor cap and rotor.   However,  on further examination, you could see sparking around the #6 spark plug.   It appeared that the miss was probably related to the damaged insulation on the suppressor.


The suppressors are available for purchase separately and just screw off.   I was given a tip on the forums to use a Stanley knife to cut away the insulation and squirt some WD40 on the thread to make sure the end of the wire is not damaged.    Once I started to cut the insulation, it became obvious that the damage was more than just skin deep, the plastic insulation was also badly cracked.


This was obviously how the spark was getting out.      While #6 was the worst, the others look fairly old and may be worth changing.


The car now runs much better.  The stumble seems to be gone and there is more power.   Not surprising since it wasn’t really running on all 6.  I will still check the cap and rotor as the idle is not perfect, and I do not know how old they are.

W126 Ignition tumbler replacement

When new, a W126 Mercedes would have come with four keys:

  • Two square headed master keys.
  • One round headed valet keys.
  • A flat ‘wallet’ key.

The master keys were designed for everyday use and opened all locks on the car: doors, ignition, glove box and boot.   The valet key is similar, but does not open the glove box or boot if manually looked.   The premise being you can keep valuables in the car while being parked by a parking attendant.   The master key doesn’t have a plastic head.  Instead, it has a small flat metal one allowing it to be kept as a spare in a wallet.

The wallet key is usually lost over the years.  I’ve owned many of these cars over the years and never had one.   Normally when buying the car used, you get some combination of other keys.    In the case of the 300SE, I received only one original key – the valet key.   The ignition tumbler had been replaced by a generic unit which no longer matched the other keys on the car.

The main problem with this was that should I accidentally lock the keys in the car or loose them, I would loose access to the car.    The simplest option would be to have the valet key copied.   However, that would leave me with two annoyances: two keys for the car, and the inability to open the boot should the central locking fail.     At this point, the simplest solution was to contact the Mercedes-Benz Classic Centre in California! For USD$51, I could get a new ignition tumbler for the car and associated master key.

Changing the tumbler is a simple, but fiddly job.     The key needs to be in the #1 position.   There is a small hole between the black collar and the tumbler where a tiny allen key or micro-screwdriver can be inserted.   This pushes back a spring that allows the collar to be unscrewed.    The collar can’t really be unscrewed by hand because of the trim, but the factory tool is basically a short section of rubber hose the same diameter as the collar.  This tool protects the paint of the collar.   I didn’t have it, and the W126 trim hides the collar pretty well, so I used medium size long nose pliers.


The installation of the new tumbler is a bit more tricky.    The process is the reverse, but I ran into a couple of problems.    I wasted 30 minutes because the small hole on the new tumbler was slightly smaller than the old.   A paper clip fitted but was too weak.   In the end I found a micro-screwdriver that worked.

The tumbler with key attached, collar and ‘tool’ all need to be aligned and then screwed on.   This took a bit of fiddling to align.    Overall, the job took me one hour and I now have a single key for the car, at the expense of about AUD$100 (including shipping) and a few scratches on the black collar.

Back behind the wheel of a W123

Today I got back behind the wheel of my old W123 280CE.   The 15 minute and 5km drive is actually the longest I ever took in that car!  This was a car I rescued more than purchased.   The previous owner had it up on ebay with no reserve, had mis-spelt Mercedes and it was claimed to have a leaky radiator.   Despite sitting in a muddy front yard, it didn’t look too bad a car and so I became its owner for $830.

I trailered it back to my warehouse and straight away I noticed that while it looked a bit dilapidated, it seemed like a car that had been well looked after until only a few years go.    Also, there was nothing wrong with the radiator at all, the water leak was coming from the water pump.    This was actually good news as while the labour is much higher on the water pump, the parts are much cheaper!

In the end I replaced the water pump, new ignition tumbler, had a small rust hole cut out and generally got the car working again.   I then sold to my brother who is a fan of the model and had recently written off his 5-Series.  In the almost 3 years since he has put almost 20,000km on he car.   Not bad for a car that was practically dragged out of a ditch.

Today, I had to go and collect the car as the garage it was stored in needs to be painted and my brother is at sea.    On the drive home, I was reminded what a great car the W123 is, particularly the coupe.   Its comfortable, nimble and stylish.   Despite the ruined looking exterior, the drive train of this car is very strong and the 328,000km engine is smooth and powerful, even detuned via ADR27A.   This car does need a few things to make it more pleasant to drive though:

  • The steering wheel is coming apart and needs replacement
  • The handbrake handle has broken in two
  • the passengers window switch is broken
  • The throttle linkage needs checking and lubricating
  • Due for a service

W123’s are still relatively inexpensive in Australia and represent a good entry level classic Mercedes.   I should know, my first Mercedes was a W123 230E and I had that car from 1997-2002.


Tall drivers can comfortably drive a Series 1 E-Type

Pretty much all the buyers guides I read when researching E-Types say that drivers over 6 feet tall should avoid SWB E-Types.   This means they are allegedly restricted to the S1 2+2, S2 2+2 and all Series 3 models.    I was never a fan of the styling updates to the E-Type as it aged, so was keen on an early car.   I also didn’t want an automatic so that left the S1 2+2 manual as my primary choice.

There were a few problems with that approach.   Firstly, at the time I was buying my car (in the United States), 2+2’s were not particularly valued by the market, so most of them were in pretty rough shape.   Given it costs the same to do up a rough FHC as a 2+2 and the FHC is worth double it was easy to see why.    I also would have been spending 20% of the purchase price on shipping back to Australia when I returned, and while I find the S1 2+2 and attractive machine, it just wasn’t the same as the OTS or FHC.

Reading the definitive guide to the E-Type I also noticed that Lofty England ran an OTS and didn’t seem to have too many problems.   He was 2cm taller than I am (196cms – 6’5″) so I tried a couple of FHC and OTS models.    I tried the 4.2 liter models for a few reasons; The seats were described as much better for tall drivers, they have much better brakes and a much better gearbox.   Surprisingly, even though its a little tight getting in and out of the car, it was quite comfortable.   The seats are quite comfortable, and there is plenty of legroom with the seat pushed as far back as it goes.

On the downside, your head is pretty much touching the ceiling in the FHC, and does touch it in the OTS with the roof closed.   To operate the pedals correctly I wear special narrow shoes or drive barefoot.     While it is not required, I also have a 1″ smaller steering wheel which is more comfortable.    In addition, when changing gears your knee hits the indicator stalk, so I have bent this back a little.   Still not quite enough, so will do more.

In summary, while the car is obviously designed around a smaller driver, a Jaguar E-Type can be driven by a tall driver.   And quite comfortably.    I’ve had my car since 2010 and still enjoy driving it.  Since I almost never drive the car with the roof closed, the lack of headroom is not a problem either.

The first photo shows my car with the smaller wheel and the second photo shows the stock wheel.

S1 OTS with small wheel

Stock wheel

Traction Avant drivabilty improvements

The Traction Avant had a number of small issues that were impacting the overall drivability of the car.   The car is now much nicer to drive after resolving them.

  • The original engine driven fuel pump had been bypassed by a very noisy electric pump
  • There was severe vibration on braking
  • Front suspension was worn
  • Valves were out of adjustment on #2 causing poor running and smoke at idle
  • The gearchange mechanism would occasionally get ‘stuck’
  • The gearbox had a bad oil leak

All the work on the car for these jobs was done by Jason at Pallas Motors.  I was able to source all the parts I needed from CCOCA, which makes keeping an older car like the traction on the road much easier.

The traction was originally fitted with a mechanical fuel pump that is driven by the engine.  For one reason or another this had been bypassed by a very noisy electric pump.   These are often fitted because starting can be hard with the mechanical pump, but the pump is fitted with a primer lever to pump additional fuel up the carby if the car has been sitting for a while.

The gear change rods linkages were fairly worn and these were tightened up to improve the gear change as well.

Fuel Pump

The vibration on braking turned out to be number of factors.   The front suspension was fairly worn and was partially rebuilt with upgraded upper control arm bushings.   These are uprated units that can use rubber bushings instead of the original brass.    In addition, adjustable ball joints were fitted.   The originals require shims to set up.

Upper control arm bushings

Ball joints

The next thing that was contributing to the vibration turned out to be a bent wheel.   Luckily the spare was very good so this was changed.

Finally, the valves were adjusted which fixed the low compression on #2 and the gearbox removed and new output shaft seals fitted.   This seems to have fixed the gearbox oil leak.


All in all the Traction is starting to drive as well as it looks.   Its not perfect, but its a hell of a lot better than it was before this work was done.

Troubleshooting W126 Climate Control

When I purchased my 300SE, the A/C worked well.   I assume the overall Climate Control system did too.  I never did test anything more than max A/C as the weather was very hot.  Everything seemed fine, except for the little aspirator fan which was noisy.  Unfortunately 3 weeks after purchase, the A/C stopped working.    I was sitting at red traffic lights and adjusted the settings and it went warm.    This indicated that it was probably not a leak in the system somewhere.    Just to be sure, I had the system checked and it was not low on refrigerant.

The first thing I tried was changing the Climate Control Unit.  This is the push button unit in the dash and they are known to cause erratic climate control if they start to fail.   I was able to purchase a used (but untested) unit for $25.

W126 Climate Control Unit

This change did not seem to make any difference.  I noticed that the compressor was never engaging even when on max cool.  Therefore, the next thing I tried was removing the Klima relay and bridging pins 5 and 7.   The Klima relay controls the A/C compressor and determines when it should engage.   It uses various sensors to control the engagement of the compressor as well as the cooling fans.    This eliminates any of the sensors.    Bridging these pins should bypass all these sensors and simply apply 12v to the compressor clutch.

Doing this and starting the car did result in the compressor engaging briefly.   I even got a bit of cold out of the system!   However a few minutes later fuse 5 blew and the Climate Control System shut down.      Fuse 5 controls most of the climate control functions (except the blower motor), so the next logical step seemed to try and eliminate what could be causing it to blow.   Next thing I tried was to disconnect the mono valve and the Aux water pump.

The Aux water pump is a small pump that increases the flow of hot coolant through the heater.   These pumps are known to draw too much current as they age and are really not necessary in warm climates.    At -20C, having the extra pump does ensure hot coolant from the engine reaches the heater faster.   The mono-valve is used by the climate control system to control how much coolant comes into the system.   (i.e. none for max cool and full flow for max heat).

Fuse 5 still blew, despite eliminating the aux pump and mono valve.   This time, It happened even before I turned on the engine.   Next step may be to test the compressor clutch with an external power source.   This would eliminate some problem with the car’s wiring.

The Mercedes W126 in Australia

Despite the newest examples being almost 30 years old, the Mercedes W126 is still a fairly common sight in Australia.   Wheels Magazine awarded it the car of the year in 1981, a controversial choice for such an expensive car.   They were popular both with private buyers, and the limo trade who racked up big mileages.   30 years later, good examples still change hands for reasonable money.  The W126 still make a great daily-driver – comfortable, safe and reliable.

The W126 (along with the R107) was also one of the most commonly private imported models with the shortsighted decision by Mercedes-Benz Australia not to import the higher powered 500 models from 1981-1985.

Officially, the following models were imported:

Generation 1:

  • 1981-1985: 280SE
  • 1983-1985: 380SE
  • 1981-1985: 380SEL
  • 1982-1985: 380SEC

Generation 2:

  • 1986-1992: 300SE*
  • 1987-1992: 300SEL*
  • 1990-1991: 420SE
  • 1986-1991: 420SEL
  • 1986-1991: 560SEL
  • 1986-1991: 560SEC

With the Advent of Generation 2, Mercedes Australia learned their lesson and included the 560 models in the line up.      Certainly during the first generation models, a large number of 500SE and 500SEL models were privately imported.   This did not stop completely during the late 80s but the demand slowed down significantly as the flagship could be purchased locally.

The officially imported models generally had high specifications, especially the v8s.    Most were equipped with self levelling rear suspension and options such as power windows, Air conditioning, cruise control etc.

The misguided ADR27A regulations had a profound impact on some models, especially the 280.    The M110 280 engine is of a twin cam design and suffered badly from lower compression, retarded timing etc. Not only did these regulations affect power, they also significantly increased fuel consumption.  For some reason Australian 380’s were delivered with shorter rear end ratios than other markets, perhaps due to the very low local speed limits.

The 380 that was found in Australian delivery cars is often mistaken for the low power version found in the USA models.   This engine had a single row timing chain for 1981-1983 and only about 116KW.   It is also found in Japanese spec cars but should not be confused with the version that was actually imported into Australia.   The AU spec engine was quite similar to the rest of world version.

Australian Specifications

EngineAustralian Performance (KW)Worldwide Performance (KW)
500 v1N/A177
500 v2N/A180-195

A local review can be found here.

Imported cars carried the specifications of their home market where UK, HK and Sing cars had the high powered engines and Japanese cars were more like Australia.  The W126 was also built it South Africa so those cars vary more but engines were generally free of pollution controls.

Today, the second generation models are the most popular and Australian delivered cars command a premium.  On the other hand, some enthusiasts seek out the higher power imported 420, 500 and 560SEC models, especially the later ones with 10:1 compression.

* Models sold in 1992 were run out 1991 models.

W126 Odometer Repair

My ‘new’ 300SE suffered from a common problem with Mercedes of that era, a non functional odometer.   The mechanical odometer is driven by a small electric motor instead of a traditional speedometer cable and associated gears.   This is because the speedometer is electric yet the odometer is mechanical.   This combination was common in the late 80s and early 90s before cars moved to fully electric speedometers and odometers.    The Series II W126 uses a VDO odometer unit shared with many Mercedes and BMW models of the era.     There are a number of articles on the internet that already cover W126 Odometer repair, however it took me a while to sift through them all.   This was one of the best.

The most common point of failure is a set of small gears that connect the electric motor to the odometer.   They are made from a very soft plastic to ensure noise is not transmitted to the cabin.   Over time, they loose teeth which stops them from working.     Replacement of the gears is a fairly simple procedure.   There are a few different companies who can supply the replacement gears – I got mine from Garagistic.

Removal of the instrument cluster

The W126 instrument cluster is simple to remove.   The cluster is only friction fit in the dash, and unlike some models the steering wheel does not need to be removed.   The official procedure calls for two special hooks to drag out the cluster.  Some people have made their own copies of these hooks. I found it easier to remove the drivers side speaker and simply push it out from behind.    There are many different connections to the cluster, and the trickiest part is removing the ones with the least slack first.  I found this was the vacuum line for the economy gauge.  That line is friction fit into its rubber tube.

Dismantling the instrument cluster

The speedometer is removed from the rear.    The outside temperature gauge is removed first.    There are after market replacement units available although I do not know their quality.   They are available in Celsius and Fahrenheit.


Next the plastic housing is removed.   Care needs to be taken with the speedometer face and needle!   This allows access to the rear of the speedometer.    It appears that the circuit board can be removed from the speedometer, but it doesn’t easily.   Its not really necessary, as once the back cover is off, the odometer gears can bs seen on one side and their cover removed.     From here the Garagistic instructions are useful, even if they are for a BMW.

Replacing the gears

The gears are easy to remove, and my small gear was pretty much disintegrated.   The only slightly fiddly job is that there is a metal bushing that also needs to be removed as the new gears do not need it.  The first photo shows two of the three gears removed and the second shows the new gears installed.

Old gears


Some people recommend some grease to ensure the gears are silent.   I didn’t have any on hand, so I’ll need to see if they are annoying and I need to remove the cluster and add some.   There was also a 4th tiny gear in the pack I didn’t seem to need.   I am not sure if this is for another model, or I missed it.   Re-assembly is simple and only takes a few minutes.   In conclusion, the final  step is to see if my W126 odometer repair worked!

The 300SE strikes back

My ownership of the 300SE had been off to a good start until 3 issues reared their ugly head in the last couple of days.

As outlined in the last post, the first issue was the A/C stopped blowing cold.  I already knew I had to do a few things for the climate control –  I could hear the little aspirator motor rattling away behind the glove box.    The aspirator motor is basically a small fan that blows air from near the dome light down to a temperature sensor.   That sensor is used for the climate control.   I’m a little perplexed as to why Mercedes didn’t just have the sensor near the dome light.   The added tube and motor seem overly complex.    The aspirator motor should not cause the A/C to stop functioning altogether.   Therefore, my assumption is that the aspirator needs to be replaced, and the A/C needs a leak repaired.

Secondly, I was in a minor accident in the 300SE.  The car was not badly damaged, which given its value is important.

AccidentHopefully it can be repaired via insurance without undue cost.

Finally, the water pump appears to have given up the ghost.  Driving home, on a fairly cool night, the temperature was steadily rising.   Moreover, it would rise alarmingly while stationary.   I stopped at a service station to check, and took in the sight of the new green river emanating from the 300SE, gently meandering its way over the concrete forecourt.     Needless to say, this was not a river I wanted to see.     I was able to top up the water sufficiently to get home.

Once home, I looked under the car to discover the source of my new river.   Surely enough, it was dripping down off the sump, leaving its residue behind.   My assumption is that the water pump has packed in and is leaking as much water as it is pumping.   The water pump is a painful job on the M103, and I don’t think I will get the time to do it.   I will probably pay to have it done along with the A/C check and re-gas.    As the say, there is no such thing as a cheap Mercedes.


On a more positive note, the car has responded well to the transmission service, with smoother gear changes.   It also seems to be selecting the ‘right’ gear more.

300SE servicing

The 300SE didn’t come with much concrete service history.    I started a full service on the car to establish a baseline.   This will allow the car to be properly maintained to the factory schedule.    The service items arrived this week, after a quick call to MB Spares in Canberra.

Box of goodies

So far I have done the following:

  • Oil and filter change
  • Renewed spark plugs
  • Transmission oil and filter change
  • Differential oil change
  • Power steering oil and filter change
  • Removed the after market chrome wheel arch trims

Still to do, is both petrol filters, air filter and to properly flush the power steering.   This service I was only able to replace the oil in the reservoir.   I forgot to order the right oil but the oil for the rear suspension also needs replacement.   The car is fitted with rear self-levelling suspension that requires a Mercedes hydraulic oil.   This suspension is based on the design used in the Citroen DS.



Examining the car, it looks like it has been generally well looked after.  It has a new radiator and back half of the exhaust system.   It also would appear it has a refurbished or new A/C compressor.  However, from speaking to the previous owners the last service was done by an ultra-tune rather than the normal Mercedes specialist and it shows.   The car was fitted with resistor spark plugs.  On a Mercedes of this era, non-resistor spark plugs are a necessity as the leads have resistance built in.   Adding resistance via the spark plugs results in a weak spark.    The car has more power and runs better with the proper plugs.

Despite improving the car I had a setback today as the A/C stopped working.  It went from working well to warm air almost instantly.   My assumption is that the system developed a major leak, although I have not yet looked into it closely.  I checked the fuses first, to rule that out and noticed I am missing a relay.   It would appear it is for the high speed on the auxiliary fan.


I don’t know why it was removed.   I can only think that either it was blowing the fuse on high speed, or another relay that was more important failed.     Finally, I also noticed a bad bushing had caused the height corrector on the rear-self levelling suspension to disengage.  I was able to replace it temporarily until I can get a proper bushing.

Height corrector

All in all, the 300SE looks like it will be a good daily driver.    Next step is to finish the service, and fix the broken odometer.  The A/C is also important, but beyond my capabilities.