I figured this was a good idea, because even on a warm (e.g. 28c) day, the car would run a bit over 100C.   Nothing wrong with that temperature, but I want to to be able to confidently drive the car with the A/C on in 40C weather, and that doesn’t leave a massive margin.

I looked into the fan clutches, and while there were cheap ones available for very little money, I had no confidence they would last very long.   A genuine Mercedes-Benz W124 fan clutch from the classic centre was about the same price as Behr clutch from Pelican Parts.    I also wanted to order a new ignition tumbler from the classic centere, so this would combine shipping.    The part number for my W124 fan clutch was 103-200-04-22.   On closer inspection, it was made by Behr.

There is a special tool required to lock in the water pump to remove the W124 fan clutch.  I don’t have this tool, plus I already wanted to take the car to the Mechanic to replace the brake hoses and do a fluid flush.   It wasn’t clear when this was last done from the service history.   I wasn’t sure of the age of the hoses, the the fluid really should be flushed regularly.

I also didn’t think the brake pedal feel was quite as good as I was expecting, so it was an opportunity to check the pads too.   Turns out they were fine, so at least I have a spare set on hand.

Before I sent the car in, I noticed the rubber grommets on top of the brake fluid reservoir were quite old and cracked.   These had prevented me from using a vacuum bleeder on the W126, so I swapped them out.    For some reason, the brake fluid light is now always on.  I’ll have to check them and make sure I put them on properly.

The other thing I wanted to do myself, was make sure the coolant level was correct.   The reservoir was filled right to the top even cold.   I assume that when the car gets quite hot it would place undue strain on the cooling system.  To be safe, I removed some coolant to get the reservoir to the right level when cold.

I had also wondered if this extra pressure might be why the low coolant light went on after the car warmed up.    Turns out, its not, and my next step is to change out the sender unit.

After all this, what were the results of my W124 fan clutch replacement?   The car was better, but not as good as I hoped.   Running temperature was a little lower (just under 100) and the electric fan didn’t cycle quite as much.   The most concerning thing, is that the temperature was at its best at about 70-80km/h.  It actually went up at 110km/h.     I could also hear the fan clutch roaring at constant freeway speed, which it shouldn’t.

My next step will be to change the thermostat.  I have spares on hand. Plus, Its a cheap and easy fix before I start to worry about things like radiators and water pumps.    Not sure what is in the car, but I plan to use an 80C thermostat.   I think 87C may have been standard, but I prefer 80.    I find A/C performance with R134A starts to degrade when the coolant temperature is above 90C.

The post W124 fan clutch and other cooling system improvements 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.

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