It’s been a while since I’ve been able to write, as after work hours my focus had been on organising the MBCV 2025 Mercedes-Benz Concours d’Elegance. As the event occurred on March 16th, I now can write about engine work undertaken on my 450SE late last year.

My mechanical knowledge is limited, but I’ve known since I acquired my 450SE that I had a problem in the top end of the engine. There has always been a mechanical ticking noise when the M117 4.5 engine was warming up and even when warm I could often hear a faint ticking noise.

After procrastinating for years, I was determined to fix the issue, so took it to my mechanic, who promptly diagnosed worn rocker arms, and scoring on the camshafts.

You can see a trough where the rocker is worn, pitting in the chrome cap. It’s not typically to see this wear on a healthy engine.  It is usually observed on cars that have had dirty oil, poor oil supply, or a general lack of maintenance. In my case, my 450SE was laid up for many years, prior to purchasing. I suspect there was a lack of maintenance, contributing to this problem and expensive fix.

You can see the deep pitting on the chrome cap. This was the worst of all rocker arms, but there was wear on most of others.

You can see the scoring on the camshaft lobes.

What’s a rocker arm? In an overhead cam engine, the camshaft must have something to push on to actuate the valve. The rocker arm is somewhat the sacrificial piece of metal that goes between the valve and the camshaft. Symptoms of worn rocker arm wear is a deep knocking noise. Apparently, the nose is more persuasive of bigger engines, V8 engines as they have short stubby rocker arms.

I have a great relationship with my mechanic, he provided a list of parts required and asked me to source them. It took me sometime work through and order what was required, sourcing them from Pelican Parts and Niemoeller.

The other task was to get both the camshafts re-ground and hardened. I used Tighe Cams for this work, as they came highly recommended from an MBCV member. The work cost $850 and took them about a month to complete. The camshaft work was excellent and as it was the last of the parts required, so the engine could now be setup.

Luckily, I had ordered two new sprockets, as the teeth on the original parts were quite worn when compared to the new sprockets. A few years ago, I had replaced timing chain, tensioner and guides, so there was no need to do this this time.

My mechanic had a set of various sizes of valve adjustment shims (also known as buckets), as we weren’t sure what sizes to order. To be my surprise, every shim required was 5.1mm, meaning there wasn’t much valve wear.

Once the work was completed, I was stunned at how much quitter and refined the engine was, especially at idle. As I had nothing to do within my ownership, originally, I just assumed the roughness was normal.

Was it worth it to do this work, absolutely, as every time I drove the car prior, I would hear the ticking noise and would just get annoyed that the car wasn’t right. Many of you will know what I’m talking about.

Author:  Nick Gruzevskis is a contributor to classicjalopy.com, and the custodian of a great collection of classic and modern cars.  Links to some his other articles can be found here

The post Guest Post: W116 450SE – M117 Rocker Arm Wear appeared first on Classic Jalopy.

While the temperature itself is well within spec, given the day wasn’t really that hot compared to days in the mid 40s we get here in Sydney, I wanted to do something about it.   Additionally, the air conditioning doesn’t cool properly when the engine is at those sort of temperatures.   This is presumably due to the R134A gas not being as efficient as R12.

The first step was to replace the radiator cap as it is likely not holding pressure properly.    This is a simple fix.   I know the radiator works properly as the engine was running too cool in winter before I had the thermostat changed.   In hot weather the car has two systems to keep cool.   The first is the M117 fan clutch.    The second is the electric auxiliary fan.  The focus of this article is the fan clutch.

On older cars, the fan is connected directly to the water pump and spins at the same speed as the engine.   This wasteful as most of the time this much air flow is not needed.   The fan clutch assists here by allowing the fan to spin slower under normal circumstances.  However, when the temperature reaches a prescribed level the fan can spin faster.    It generally won’t spin at a 1:1 ratio but will be limited to a particular RPM that is efficient for max airflow.

My 560SEL is equipped with such a fan clutch, as are other W126 models.   When the engine is hot, you should be able to hear the fan roar when you rev the engine and I never heard this.   Additionally, if you turn the car off when the engine is very hot, it should be hard to spin the fan.   On my car it wasn’t.   As the M117 fan clutch in my car was the original unit, it seemed like a good idea to change it.

It is a very easy job.   The M117 fan clutch is held on by four 10mm bolts.   There is no need to remove the radiator or even the top radiator hose.  All that is required is to loosen the shroud so the fan assembly can be removed.

Once the fan assembly is removed from the car there are four more 10mm bolts holding the fan to the clutch.  I used a rubber mallet to remove the old clutch from the fan.   The new one looks a bit smaller and doesn’t have the plastic protector like the old one.   It is made in China, so I hope it lasts 33 years and 328,000km like the old one did.

The picture above shows the original M117 fan clutch, with the 1987 date on it.

Once the new clutch is installed then the installation is the reverse of the removal.   One trick I picked up on some forums was to put the lowest of the four bolts in first.   The fan assembly doesn’t attach through hole – there are cut outs.   This allows the fan assembly to slip onto the bolt to locate it before the others are installed.   The photo below shows the whole assembly removed before re-installation.

I have not been able to test the success of this job yet.   It was 15C and raining today.   This is probably the last cold snap before a hot summer, so I doubt it will be long.   I also need to test the operation of the electric auxiliary fan.

The post M117 Fan clutch appeared first on Classic Jalopy.

These engines evolved over time with the final iteration coming between late 1985 and 1991.  The 560 was the largest M117 engine offered, although to be pedantic it is actually 5.5 litres.  The M117.968 was offered in in the second generation W126 and and is the subject of this article.   The M117.967 was offered in the R107 for USA, Japan and Australia with emissions controls.  It had less power than the contemporary 500 engine.

The story goes that Mercedes-Benz were concerned that the introduction of the BMW E32 7 series with its 220KW V12 placed the W126 at a competitive disadvantage.    The W140 was apparently delayed to respond with a V12 and the 560 was a short term competitive response.  The 560 is a longer stroke version of the 500.   At the same time larger valves were also specified.  The 560 offers more power than the 500, although the 500 has the reputation of being the smoother engine.

To meet the E32’s specs a high output version of the 560 engine was offered with 220kW.  This engine had a raised 10:1 compression ratio, different cams, ignition timing and an improved exhaust system.  It was coupled with a 2.65:1 rear end, allowing it to deliver similar performance to the E32.   The 2.65 contrasts with the 2.24 ratio used on the 500, and the 2.47 used on the 420.   At first, the high output version was an option, code 822.   It was offered from 10/1985-9/1987 and known as the ECE version.   My 1987 560SEC is the code 822/ECE version.

The ECE version was a start, but more and more markets in Europe required a catalytic converter.   Mercedes offered two versions for this case.   The KAT version had 180kW and had the Catalyst fitted as standard.  The RUF version was set up to allow the catalyst to be retrofitted later and had 200KW.   Both of these versions ran the standard 9:1 compression.

Mercedes still faced a challenge against the E32.   Many European markets required the RUF or KAT version.   Therefore, from 9/87 the RUF and KAT versions were revised.   Compression was raised to 10:1 and other changes introduced, such as knock sensors to retard the timing when necessary.    This made the ECE version redundant, as the RUF version now made 220KW.  The RUF version could still be retrofitted with a catalyst.    The revised KAT version now made 205KW, a useful improvement.  While not the subject of this article, the compression ratio changes were also applied to the 420 and 500 engines, providing a useful power boost.  The 10:1 engines either have HV or E10.0 after their engine numbers.   These improvements were not made to the engines for very strict markets such as Australia, the USA and Japan.

At the same time, code 822 was withdrawn.  This makes it harder to work out what version of the motor is installed in a given car.    You have to know what version was offered in each country and then check which country the car is from.   The main source of high compression cars in RHD countries is the UK and Hong Kong for example.  Increasingly, EU countries required a catalytic converter.

The 560 engine also offered an opportunity to provide more performance in markets with strict emissions laws.   The larger motor still allowed good performance even when de-tuned for idle emissions.    This was particularly important in the all important US market.    The 1984-85 500SEL in US spec only managed 137kW.   The move to the 560 allowed power to be raised to 178-180kW depending on market.   My 1988 and 1989 560SECs were both this version.  The primary destination of this 560 was the USA, but it also formed the basis of the Australian and Japanese versions, with minor changes.

One particularly restrictive element of the US and Japanese M117 is the exhaust system.   There is a crossover pipe that joins the output of both banks of cylinders into a single catalyst.  Upgrading this part of the exhaust system is the simplest way of gaining more power of this motor.  The Australian version did not get this exhaust.

This version of the 560 was equipped with a 2.47:1 rear end instead of the 2.65 used in other 560s.  This was probably due to the US Corporate Average Fuel Economy (CAFE) regulations.   The CAFE regulations imposed fines on manufacturers based on the average fuel consumption of their entire range.

Unlike the other 560 engines, the emissions version never had the compression ratio revisions.   It was the same story with the M116 420.  The rest of world 420 had the compression rise but the emissions version did not.

It was this emissions engine that was the only 560 available in the R107 as the M117.967.   The 560SL was only offered in Australia, USA and Japan.   It is slightly lower in power than the W126 version as the exhaust was even more restricted.  This 560 is referred to as the 117.967.   The use of this engine version is why it is less powerful than the contemporary 500SL.   The big advantage of the emissions engine is that it can run lower octane (91) petrol.

There is some confusion over the exact power ratings of these emissions engines.   The USA workshop manual lists the Swiss and Australian version at 178kW and the USA and Japan version at 180kW.   However, the official spec sheet that was included for the Australian versions lists it as 182kW and with 400Nm of torque, as does the 1987 technical data book.  I am inclined to trust the technical data book and spec sheet.   The exhaust is less restrictive for one in the Australian version.  There is also no EGR.

The differences between the engine types are extensive:

Exhaust

The high output versions had ‘tri-y’ exhaust headers.   Essentially the tri-y setup consisted of four piece manifolds that joined under the car into a dual exhaust system next to the transmission.   The mid output versions had ‘euro log’ exhaust headers which was a single manifold for each side, each with a pipe under the car to the exhaust system. When catalysts were fitted, there were two.   The final option was the restrictive system where a crossover pipe behind the engine linked the two manifolds together to enter the single catalytic converter.    The KAT/RUF cars have an oxygen sensor.

The engine photo clearly shows the exhaust manifold from the ‘tri-y’ setup.

The photo below shows the setup used in the North American version and most likely emissions controlled Japanese version. The crossover pipe and single catalyst can clearly be seen.

The regular catalyst version was a bit of a hybrid of the two, with a less restrictive manifold setup.   This was also the exhaust used for the Australian version.

Ignition

All models used EZL based ignition, but the map was different.   The mid and high output models had a switch to allow the engine to be de-tuned for poor fuel.    The emissions controlled models were not switchable.    The high output motors have a more advanced ignition, and the later (post 9/87) cars have knock sensors.   As the early ECE versions do not, they require 98 octane fuel.

The ECE (Code 822) versions carried the following sticker on the radiator support:

Camshafts

High output engines have different camshafts with ECE, RUF and KAT camshafts all having different part numbers.

The ECE Camshafts have code 16/17 (Left/Right).   RUF are 24/25 and USA is 26/27.    The ECE and RUF cams have the same profile.

Other

• The strict emissions version has an air pump for some markets such as USA.
• The high output motors also have a different fuel distributor, same as the the early R129 500SL.
• All 10:1 compression engines have high compression pistons.
• The high output models have a separate oil cooler and pump.   This is located at the front left of the car.  The image below shows the extra oil cooler marked as B.
• High output models have a different (black) transmission modulator
• Transmissions were the same on all models.   Starting with the 722.323 and then later the 722.350.   The .350 transmission was improved over the 323.  I have read that the high output engines had a reinforced transmission, but have not seen any factory evidence so far.

Unlike other Mercedes engines, all versions of the 560 are good.   Even the emissions versions have plenty of power and are a delight to drive.   The M117 has an almost bullet proof bottom end, but an Achilles heel in some plastic parts in the engine.  If these parts fail, it is not economically viable to fix the engine.

The post The M117.968 560 Engine appeared first on Classic Jalopy.

Over time the plastic guides become brittle and the chain stretches.  The most likely failure is either due to a stretched chain or brittle guide, the guide breaks and causes the chain to jump a tooth.   Best case is valves and pistons meet, causing bent valves and the chain ripping a hole through the rocker cover.  Worst case is a completely ruined engine.

I’ve heard that the chain really should be changed every 100,000km.   My car has a full service history, but it doesn’t indicate if the chain was every changed.   I had this job done on both my 560SECs (also M117 engines).   Both cars were ticking time bombs – at around 300,000km they had original chains and cracked guides.

The only way to check is to remove the valve covers.  This is not a particularly difficult job on the M117:  It just involves removing the air cleaner assembly, spark plug leads and a few other pipes.   The picture below shows the chain and one of the plastic guides.   Straight away it is obvious this chain has been changed as the link is showing.   The original chains do not have the link.    The guides did not appear worn or discolored.

I know a lot of work was done to the car about 12-18 months before I got the car – at about 230-240,000.   This would probably fit in with the condition of the chain, guides and sprockets.    In this case, the chain probably doesn’t need imminent replacement, although the correct procedure is to check chain stretch which I did not have time to do.    On various forums, I have read different things about the guides.   I have heard the Febi guides are not as good as the factory guides.   I have also read that there are uprated guides available.    I have not yet had a chance to investigate either option.

I had become increasingly concerned about the timing chain on my car.   I will need to do this job in future.   The good news is that it does not appear the engine is a ticking time bomb.

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