W126 low pressure hydraulic hoses

My 560SEC has been leaking from the power steering and self leveling suspension.    In both cases, it is obvious that (at least some) of the leakage is coming from the low pressure hydraulic hoses.    It is possible there are additional leaks in the steering, but fixing this obvious one is a good place to start.

I had looked at doing this job a couple of months ago.  I quickly saw it was quite fiddly and as I was planning to use the car the next day, I decided to put it off.   Once I realized I would be removing the radiator this seemed the perfect time to do the job as there would be a little more room.   Unlike the high pressure hoses on the output side of the pump, the low pressure hoses are just standard hoses and are on the input side of the pump.

The first one I did was the power steering hose.   I had previously ordered a meter of the Mercedes power steering hose, which should be enough to do 3-4 cars.   I’ll need to do this job on my 300SE at some point.    Doing this job is a good time to change the power steering oil.  Even better, if you have an assistant to do a flush as well.   The pump runs at too high a pressure to do it on your own.

Because of the position of my A/C hose, I found it easier to remove the elbow fitting, as can be seen in the picture below.   The flexible hose is quite short and joins up to a hard one in the frame below the P/S pump.   The old hose allows for the new one to be cut to the proper size.    In the photo below you can also see the hose for the self-leveling rear suspension which is very wet.

low pressure hydraulic hoses

My hose was not in horrible condition, but it had been weeping out of the hose material.    The new hose and the size required can be seen below.  The EPC lists the exact size, and for example the 300SE needs a slightly longer one.

Low pressure hydraulic hoses

The new hose is quite hard to get on the hard line, and the clamp further tightens it on.   I am not expecting any leaks here!   I found my battery cable cutter the easiest way to get a good cut on the hose.    One of my hose clamps got broken on removal so I will need to replace it later.

The hose for the Self-leveling suspension was in a really bad way.   it was leaking quite badly out of the fabric cover, and the hose made a crunching sound, indicating that the inside of the hose had completely failed.   I found the easiest way was to clamp off the hose and cut it, so I could remove the reservoir.   As I had flushed the system recently, I didn’t plan to evacuate the fluid.

Low pressure hydraulic hoses

The bracket for the reservoir was a bit crusty and at some point I should do something about it.  I don’t think it is supposed to be painted, I think it is supposed to be anodized.    I will have to check.    The hardest hose clamp is the one that connects to the SLS pump.   I needed to find a screwdriver that was the right length and head type.   Too long and the fan got in the way.   Too short and I could not grip it properly.   I think I had nearly all the Phillips head screwdrivers in my toolbox out until I found one that did the job.

I used fuel hose as a replacement as that is basically what the braided hose is.   Again, I was able to use the previous hose to determine the required length.    It was a bit of a fiddle, but I was able to use my finger to stop the oil coming of the top of the reservoir as I turned it on its side and swapped the hoses out.     I then used the hose clamp to stop leakage until I had pushed the other end of the hose onto the hydraulic pump and tightened up the clamp.

Low pressure hydraulic hoses


I am hopeful that these new hoses will fix some of the worst of the leaks on the SEC.   Especially the SLS hose, that one was particularly bad.    I will be performing the same jobs on the 300SE at some point.

W126 radiator removal

As part of the work I have been doing to the 560SEC, I have removed the radiator.   The radiator was leaking from the top tank and appeared to be original.   It was an IMI unit which was one of the OE suppliers and had a 1987 date code on it.    W126 radiator removal is fairly straightforward.

Fist step is obviously draining the coolant, and there is a drain valve at the bottom of the radiator.     The coolant will drain must faster if the radiator cap is off.    I am really happy with how clean the coolant is, and how little residue there is in the cooling system.    A big contrast to my Citroen DS and the years it spent in South Australia.

At the top there are a couple of metal clips that are easily prized off.   Mine had gotten a bit rusty, so I will be replacing them.    There are clips that hold the radiator on, and that hold the fan shroud to the radiator.    The W126 radiator and fan shroud cannot be removed as a single unit.   The shroud must be pushed back a little so the radiator can be withdrawn and then the shroud removed separately.

There are six hoses that must be removed.   At the top there is the main hose to the motor and the small overflow hose.   They are removed in a matter of minutes with hose clamps.    As they are at the top and do not get moisture flicked up from the road they are generally in good condition.

The bottom is a different story.   There are two coolant hoses – the main hose to the engine and the smaller hose to the remote tank.   I found that my clamps had rusted in place.   For the main hose, I eventually got it free with some penetrating oil and using a socket on the hose clamp instead of a screwdriver.    In the end I had to cut the smaller hose.   I will be replacing the hoses, but was hoping to keep the current ones as spares.

The other two hoses are for the transmission oil cooler.   The end of my hoses looked really rusty and they were not wanting to move.   Given their age, I ordered some new ones and removed them at the other end which, thanks to oil leaks around the engine, were rust free.     As I was not going to keep the hoses, eventually I got the other end off after more persuasion.   Of course, removing the hoses at both ends means a big mess under the car as it is hard to catch all the oil drippage.   Cleaning up oil spills is a good use for Murdoch newspapers.

From there it was a simple matter of sliding the radiator out past the shroud.   The A/C condenser remains in place, so the freon does not need to be evacuated.      There is nothing obviously wrong with the old radiator, but the new one certainly looks much cleaner.

W126 radiatorThe radiator and shroud out of the way gives a little bit more room to replace the low pressure hydraulic hoses for the power steering and self leveling suspension.   They are both leaking and will be the subject of the next part in the series.

W126 Monovalve eliminator – part 2

My 560SEC had been leaking coolant and giving me heat when I didn’t want it.   Last week I started the repairs for these problems.   As the Bosch and Mercedes W126 Monovalve repair kit was no longer available, I have been installing the Klima Design Works monovalve elimination kit.

In the first part I removed the W126 monovalve, auxiliary water pump and other hoses.   This gave me the room to give the area underneath the heater hoses a good clean.   There were some leaves and other detritus.   Its important to remove this stuff it can cause rust.  The mud stays wet far longer than if the area was clean.

Cleaning out the heater hoses

The picture above shows the cleaned area.   It also shows the space I am going to fit the new components.   The two outputs from the heater core are seen on the right, and the hose back to the engine in the middle.    The bracket where the W126 monovalve used to go is on the left.

My plan is to use a T-piece to join the two outputs, run the coolant through the heater valve, and then place the vacuum solenoid where the W126 Monovalve used to go.

W126 Monovalve replacement

The picture above shows the setup I plan.   I have a few more hose clamps on order before I can fit this.   The clamps that went on the W126 monovalve side were too large.

A vacuum line will go from the end of the valve back to the solenoid and the whole thing will be covered up my the control box that was there before.   I used new heater hose except for the bend, which was in good shape.

W126 Monovalve eliminationOnce the new hose clamps arrive, I will finalize this assembly and then move on to changing the radiator.   The new assembly is slightly too long but the flexibility of the hoses should hopefully allow it to work.

W126 Monovalve eliminator – part 1

My 560SEC has been having a couple of problems with its cooling system.  Coolant has been weeping out of the top tank of the radiator.  In addition, the monovalve has failed, causing unwanted heating at idle.  The radiator looks either original or replaced very early in the cars life.   As these radiators have plastic tanks, I have purchased a new one to replace it.

It used to be possible to purchase a monovalve repair kit from Mercedes or Bosch.  The supply of these has now dried up.   There is a kit from a company called MTC but all the Mercedes Forums and facebook groups are litted with stories about how this part never works properly.   A friend of mine put me onto a company called Klima Design Works that offer cooling system upgrades for W123 and W126 cars.    They have a monovalve elimination kit for sale.   Their kit is focused more at the W123, but can be adapted to the W126 as well.

Monovalve elimination Kit

The kit uses a vacuum solenoid to turn off the coolant flow instead of the electromagnetic monovalve.   I especially like that the valve is closed if something goes wrong.  Here in Australia it gets very hot, and A/C is used far more than heat.

The W126 system is a bit more complex than on a W123.   For starters, the heating components are behind the first firewall and the heater core has two outputs that go into the monovalve instead of one.   Klima Design Works suggest leaving the W123 monovalve in place and putting their heater valve upstream of the monovalve.    They do suggest removing some of the components to increase flow.

Monovalve heater hoses

The picture above shows the coolant flow for the heater.  Its not 100% correct as this picture shows the duo valve for the manual climate control, but other than that, its the same.  The coolant enters the heater core via hose 68, and exits through hoses 50 and 53 where it enters the monovalve.   The monovalve controls the flow of coolant.   There is an auxiliary water pump (26) that helps flow coolant at idle to generate more heat.

Monovalve heater hoses

The hoses are exposed when one of the control boxes (that sits in the metal frame) is removed.   The monovalve is on the left, hoses in the centre and the auxiliary water pump underneath.

The simplest way to install the kit would be to cut the hose on the engine side of the auxiliary firewall (hose 68) and install the heater valve there.   That seems like a bit of a hack job to me.   I want to keep the components on the other side of the firewall as the factory did.

The advantage of leaving the monovalve in place is that the car will look more original.   Having said that, removing it can easily be reversed, and I am planning to remove it and the auxiliary water pump.   The auxiliary water pump is only necessary in very cold climates, and it is one more thing to leak and cause problems.   On the Series 1 cars it can cause major problems as it is unfused.   Best case it takes out the climate control unit.  Worst case it causes a small fire.   The Series 2 cars don’t suffer from that problem and disable it if too much current is drawn.

I am thinking of combining hoses 50 and 53 with a T-piece.    I would then mount the heater valve on this combined hose and join it to hose 59.   This would be the simplest solution.   The heater valve would sit where the auxiliary water pump used to be and the solenoid would sit where the monovalve used to be.   Other than cutting hoses (which are consumables) I won’t be permanently modifying the car in any way.

Monovalve removed

The picture above shows the removed monovalve, auxiliary water pump and various bracketry.  It is a very fiddly job removing all this stuff is there is very little room to work between the two firewalls.   Still, with these components removed there is now plenty of room for the new heater valve and solenoid.    The picture below shows an elbow piece as an example of how the hoses will flow.


Removing all these hoses is a good opportunity to clean out the leaves that have accumulated underneath the hoses.   I’ve also removed the cowl coverings to give things a good clean in there.   It was necessary to remove the control box bracketry.

July and August Night Drives

I’m a member of a few different car clubs (Mercedes, Jaguar, Citroen), but am rarely able to make events.   With a young family the times rarely work for me.   A lot of the time I spend either working on or driving my cars is late at night.   I figured I am not the only one in this situation, so after a poll of a few friends from the Mercedes club, we have started up a monthly night drive.

Not only is driving at night more convenient for me, but the traffic is greatly reduced, especially cyclists.   Obviously you have to be more aware, particularly of wildlife.   Many petrol stations are closed too.

The first one was in late July and the route was up the old Pacific Highway to the outskirts of Gosford.

Night Drive

On that inaugural drive, we had a 380SEC, a 420SEL, my 450SLC and a 280CE.   The old pacific highway is quite a twisty road and is a lot of fun even at the legal speed limit.   It was also a good run for the 420SLC with its new injectors.   That drive was pretty uneventful and we came back via the motorway.

This months night drive was around the back-roads between Dural and Wisemans Ferry.    That route is not as demanding as the Old Pacific Highway, so it was a good night to take my 250SE Cabriolet.

Night DriveThe weather was almost warm enough for top down motoring with the heater on, gloves and a hat.   On that drive we had a 280SE 3.5 (above) and a W211 E55 AMG, Audi S3 and CLA250.

Night Drive

This months was also a lot of fun, but perhaps a bit more eventful.   At the final meeting point we disturbed an amorous couple in a Ute who had to quickly get their clothes on and drive angrily away.    Secondly, on the drive back the charging light on my 250SE started to flicker on and got brighter and brighter on the way home.   After a while, I turned off the radio, but figured headlights were pretty important.

Luckily for me it was failing slowly so I was able to drive home without incident.  When I arrived back, I tested the voltages with a multi-meter.  With the engine running and headlights on I had only 11.6 volts at the battery.   With the engine and headlights off, I had 12.2.   Thankfully the 250SE does not have any sensitive ECUs etc that would not have enjoyed running with low voltage.

New Jaguar E-Type fuel pump

A couple of months back, I noticed a bad fuel smell from my E-Type.   I was able to trace the problem to a leaking E-Type fuel pump.   The car still had the original points type SU pump, which are rebuildable.   After speaking to a few people, and doing some research, I decided to purchase a new pump.   The new SU pumps are a solid state version, so no points inside.   I’ll keep the original pump with the car in case I ever sell it and somebody wants the original.

E-Type fuel pump comparison

As can be seen from the picture above, the new pump looks pretty much identical to the old one.   It is a relatively simple matter of moving the mounting brackets from the old pump to the new.   The photo below shows the brackets on the old pump before I transferred them.

Fuel pump brackets

I later learned that it is much easier if you just slip on the circular bracket without tightening it up, to locate where along the fuel pump it should sit.   I didn’t have it quite right and I had to undo it to properly locate the bracket.   These brackets are what turn the generic SU pump as used in countless British cars to the E-Type fuel pump.

While replacing the pump, I also replaced two of the rubber isolators.   The were the two for the circular bracket.   The rubber isolators stop vibrations from the pump transmitting to the car.   In the parts diagram there are supposed to be three, but the front one on my car was different – It was being used as a ground connection and there was a small rubber donut that was still in good shape.   On the other hand, the other two were in poor shape with one completely broken.

E-Type fuel pump isolators

Getting to the furthest one can be a bit of a pain.    The new isolators were actually a bit easier to fit as they had hex top and bottoms to make tightening up easier.

Once the isolators were in place, I was able to locate the circular bracket, tighten it up and then mount the pump to the car.   I sanded the washers to ensure they were really clean and then its quite simple to attach the fuel hoses to the E-Type fuel pump.   While I was attaching them, I noticed some very small cracks starting to appear on the outside of the hoses.   They do not leak, but before I put all the trim back in the car, I will order some new hoses and replace them.

E-type fuel pump testing

A few quick tests showed no leaks.   Firstly when turning on the ignition and priming the pump.   Then while starting the car and letting it idle.   Finally driving for 10 mins and pulling over to check for any fuel.   All good.

Surprising the new E-Type fuel pump has impacted the driving experience.   The car has better throttle response if you accelerate in top or third gear.   Before it felt like it was pinging, but actually the old pump might have been starving the car of fuel?   In any case the car is better and I was able to re-advance the timing a bit on the small adjustment wheel on the distributor.   The engine is still not as smooth as I would like.   I notice the motor mounts look quite flat, so this is something to look at.   It may also need a tune if the fuel pressure was off before.

R/C107 Differential Ratios

The R/C107 models had an extremely long production run – 18 years.   There were a variety of different models and specification changes.   This included the differential ratios that can have a big impact on the performance and economy of the vehicle.

In compiling the table below, I have tried to research the various country specific variants.   It is possible I have missed a few.  Please indicate in the comments below if that is the case.

The SL and SLC of the year had the same mechanical specification (at least during the SLCs production run).   The only exception was the 450SLC 5.0 where there was no equivalent 450SL 5.0 until the facelift and the 500SL model.   
R/C107 Differential Ratios

Many of the same aspects that were covered in the W126 table are applicable here.   As with the W126, the V8 models received the larger (1.3l) case.    Also, as with the W126 models, Mercedes-Benz went on a fuel efficiency drive during 1981 which is why the V8 cars got revised ratios.   The project was called the “Energy Program” and included other changes such as the revised Bore/Stroke of the 380 engine.

Early in the first generation production, the 450 models moved from a 3.07 ratio to 3.06.   This was achieved by changing from a 46:15 gear set to a 52:17 gear set.   This was more of a minor specification change than any real impact on the car.

From the long term ownership of a 450SLC, I think the chosen ratio works well for that car.   I’m not as sure of some of the other ratios.   My view is that some of the later ratios were too tall.   They probably worked a bit better for the home market on the Autobahn than in countries with lower speed limits.

Model / YearDifferential RatioSpeed at 1,000 RPM (4th)RPM at 100km/h
First Generationwww.classicjalopy.com
280SL (107.042)
280SLC (107.022)
5 Speed Manual (to June 1976)
RSA (to May 1976)
280SL (107.042)
280SLC (107.022)
350SL (107.043)
350SLC (107.023)
450SL (107.044)
450SLC (107.024)
To Dec 1973
450SL (107.044)
450SLC (107.024)
From Jan 1974
450SLC 5.0 (107.026)2.7244.52247
450SL (107.044)
450SLC (107.024)
USA 1980
Second Generationwww.classicjalopy.com
280SL (107.042)
280SLC (107.022)
380SL (107.045)
380SLC (107.025)
AUS, SE 1981-1985
500SL (107.046)
500SLC (107.026)
380SL (107.045)
500SL (107.046)
Third Generationwww.classicjalopy.com
300SL (107.041)3.4635.32833
560SL (107.048)
USA, AUS, J only
420SL (107.047)
500SL (107.046)

Mercedes-Benz Australia price list – April 1982

In April 1982 Mercedes-Benz was pretty much king of the hill when it came to mainstream luxury cars.   Rolls Royce was in a league of its own, and Jaguar was at its quality nadir.   BMW were just releasing the E30 which would propel them to a leadership position in the small, luxury market.  They still could not touch Mercedes-Benz in the mid or upper tiers.

As a result, Mercedes were able to charge premium prices for their offerings.    This was before the introduction of fringe benefits tax in Australia, so many of these cars were purchased as company cars with big tax benefits.

To put the prices below into perspective, at the same time AV Jennings were advertising a new three bedroom home that could be built on your block for only $29,950.   This was about the same price as a 230E before sales tax.

The 1982 range was quite small given how successful Mercedes-Benz were at the time.   The highly successful 230E had been able to effectively replace the 230, 250 and 240D in the line up.   They were also only offering three S class models.   I suspect there was a bit of complacency in this line up.  The grey market was thriving with private imports of the 500SE/SEL and SL models happening in big numbers during this time.

It wouldn’t be long before the lineup would be much expanded with the successful W201 190 series, and the expanded range of the W124 and second generation W126.   In the short term, the 380SE would also soon join the range.    For April 1982 though, you could only get the the V8 in the long wheelbase or the SL.   In addition, there was no manual transmission at all in the line up.   It would take the W201 to add this back.

The next 9-10 years would see significant price inflation.   Compare this to the 1991 price list.

April 1982 price list header

ModelTransmissionTypeList PriceSales TaxRec Retail price
300TDAutoWagon 5 Seat$35,462.35$4,585.65$40,048.00
Wagon 7 Seat$37,287.10$4,821.90$42,109.00
280TEAutoWagon 5 Seat$38,147.62$4,933.38$43,081.00
Wagon 7 Seat$39,972.37$5,169.63$45,142.00

Yorkstar Motors – December 1969 Price List

I recently came across a price list from Yorkstar Motors, dated December 1969.   Yorkstar motors were at that time the main dealer in Sydney and I think they had something to do with the overall importation of the cars.  This era Australian delivery cars have a Yorkstar motors tag on them regardless of where they were sold.

Unlike in later years, nearly the whole range was offered in 1969.   It was only have the ADR regime became stricter in the mid 60s that Mercedes-Benz started to limit the vehicles they offered in Australia.   This was probably due to the cost of compliance.

The only models missing off the list were the 200 and 200D W115 models, and the 280SE 3.5 Cabriolet, which would be sold in later years.   The entry level W115 cars were probably considered too slow and really for the taxi market.  Mercedes were not a supplier of Taxis in Australia.   Locally built cars dominated the Taxi market.

One thing that jumps out to me is how much more expensive the 280SEL is over the standard 280SE.  No wonder they didn’t sell many of them.   While cars like the W109 were much more expensive than the W108, you at least got major differences to show for it.   The 280SEL was a simple stretch of the 280SE.   From what I gather, the body shells were modified manually, which might explain the higher price.

It is also interesting how much of the range was offered with the choice of an automatic or manual transmission.   It is extremely rare to find a manual transmission car from this era, outside the SLs.   Even the SLs are mostly automatic.   It was only the M100 cars that were not offered with a manual.

For other Australian price lists, please see November 1966 and July 1991.


ModelPrice (Manual)Price (Automatic)
280SL Roadster$11,163$11,741
280SL Coupe$11,340$11,918
280SL Coupe 2+2$11,422$12,000
280SL Coupe/Convertible$11,718$12,296
300SEL 3.5$13,908$14,486
300SEL 6.3N/A$20,850
280SE 3.5 Coupe$15,306$15,884
600 PullmanN/A$35,153

MBCNSW Drive to Bilpin

Today I joined an event with the MBCNSW for a drive to Bilpin.   Bilpin is to the West of Sydney and is half way up the Blue Mountains.   It is know for its Apples.   The purpose of the drive was to raise money for one of our club members, Sam.  Sam is the proprietor of the Bilpin Apple Pie Cottage, our destination.   He suffered quite a loss during the big fires last summer, losing buildings and part of his stock.   It was then a long time before he could start trading again due to clean up.   Finally, when things were getting back to normal COVID hit and there was even more impact.

This drive was actually rescheduled from earlier in the year.   On the day it was supposed to happen, there was a big storm and the power was out, causing the original event to be postponed.   I had gone to the meeting point and almost drowned in the 10 meters from the car to the McDonalds.

Today the weather was much better, if still a little wet.   This time I brought the whole family – Apple Pie and Ice Cream is a powerful draw card for small children.   The drive to Bilpin up Bells line of road is quite nice and the traffic was fairly light.    As I had the whole family, I brought the 300SE.   It was a good run for the 300SE as it normally gets used for very short trips around my house.

There was a pretty good convoy of cars for the drive to Bilpin, including a W108, a couple of W126s (my 300SE and two 420SELs), 107, 114 coupe, a W140 in a fairly unusual colour, an A124 and some more modern cars.   Also in the line up was a McLaren.

The whole family enjoyed the pie, and there was a raffle draw where I won a voucher for some car detailing.   As I’m terrible at car detailing, I am sure this will come in handy.

From there, the rest of the group did an extended drive up to Mt Wilson.   We peeled off and went for a walk in the nearby Blue Mountains Botanical gardens before driving back home.