W124 fan clutch and other cooling system improvements

When I first got my 300TE registered, I had the A/C regassed as it wasn’t very cold.    That made a huge difference as after that the car was ice cold.   According to the service history, it had been a couple of years since it was last done, so it was probably about due.    At the time, my mechanic suggested I replace the fan clutch, as the electric fan was cutting in quite a lot.  He didn’t think the mechanical one was getting enough air through the condenser.

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.

W124 fan clutchThere 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.

Coolant reservoirI 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.

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