W124 Viscous fan clutch fitting

millo777

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I've just ordered a new viscous fan coupling for my W124 and need some help on how to fit it.

For ref, GSF stock Sachs or Febi Bilstein at 35 +vat and ecp stock OTSA at 52 + vat. Having never heard of OTSA I went with the sachs options.

From what I can see it "should" be fairly simple. Loosen the belt tensioner, remove the belt, undo the nut holding the fan in place, remove and replace.

However, nothing is ever that simple with this car.

Without the special tool, is there any established way of stopping the fan pulley turning when trying to undo the nut on the fan?

Also, is the nut a regular or left hand thread? from looking at other threads, it looks like the diesel engines have a left hand thread and the petrol (which I have) use regular threads. Is that correct? I'd hate to spend 30 minutes tightening the nut before figuring out I'd made a ****** of the whole job.

Thanks in advance,
James.
 

kth286

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it is awkward.

needs a tool fabricated, made from a rod to go into a groove in the back of the pulley to stop it rotating.

Haynes manual will be useful to you, from Halfords.

DO NOT lay that fan coupling down. They should be stored and freighted in upright position.

What makes you think your fan has gone wrong ?
 

grober

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The left hand thread nut will have little notches cut in the middle the nut angle edges. Bodgers clamp the drive pulley with vice grips but it tends to chip the pulley edges. You can make up a locking plate from mild steel.
 

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millo777

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@kth286, I was stuck in a motorway tail back on Saturday morning and the temp just kept on rising, getting very close to the red line. I checked the fan yesterday and it spins very freely, over runs when the engine stops, and this morning I got the car up to temp, between 80 and 90, and then stuck a folded up news paper into the fan with the engine running. Not only did it stop dead, it was actually possible to spin it i the opposite direction with the engine still running......it's toast.

@ Grober, I did see your post in a different thread, if only you didn't live so far North and I could blag it from you for the day! I don't think I have the patience or materials to replicate the tool you fabricated. Fair to play to you though sir, I always like to see an ingenious solution. Maybe you could trace the outline on an A4 sheet and scan it, then others could use yours as a template to make their own?

I do have the haynes manual, which is really why I posted. Haynes says to use a 4mm rod to lock the fan pulley, which doesn't sound anything like the tool Grober has made for the same job.

The part should be here tomorrow and I'll have a go then and report back.
 

kth286

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@kth286, .....it's toast.

Based on what you said, that is not necessarily true.

Also what Grober said is not applicable to the 320 (104) engines.

I may be true for the smaller 220 engines.

I will see what I can find regards the 'kick-in' points (in terms of temp), but it is supprisingly high.
 

WDB124066

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It should be fully locked up at 105 DegC & it starts it's engaging function at 89 DegC IIRC.....??? The 124 has a unique temp range, different from the S Class 320 engines, and higher.

BUT, if there is next to no flow from it at idle that is not good. You can hold your hands above and slightly rearward from the fan at idle and it should feel like a hair dryer at full noise.
 

312 Sprinter

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They tend not to be that tight, unless some numpty has used loctite. I use a sawn off spanner. With the belt still on give the spanner a sharp whack with a hide hammer and the coupling will pop loose.

Then change the belt. You may well find the belt tensioner rattles afterwards; they wear. Release it by rotating it anti clockwise on its spindle. You'll need a star drive socket. You can lock it using a pin, it's preferable to just letting it unwind.

DSC_5515.jpg
 

grober

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Based on what you said, that is not necessarily true.

Also what Grober said is not applicable to the 320 (104) engines.

I may be true for the smaller 220 engines.

I will see what I can find regards the 'kick-in' points (in terms of temp), but it is supprisingly high.

You are correct of course- from the posters description I was assuming the viscous coupling was attached to the water pump pulley via a large LHT nut on the rear of the unit- its LHT to stop it unscrewing with the rotation of the engine- in some instances of course the VC is held on with a large machine screw at the front. :eek:
 
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millo777

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@kth286, good point re the kick in point. I'll check it again today at 90 before fitting the new unit.

When the car came close to overheating, it came back to 80 within a minute of driving on open road. On that basis it seemed unlikley to be an issue with the thermostat or water pump. I will double check the fan though just in case.

The bolt holding the fan clutch on is of the allen key variety. Typically I can't find my sockets to fit these (Most of my stuff is still in a self storage unit), so I need to buy one of the right size for this job. Can anyone confirm what size it is?

@312Sprinter, are you saying it's o.k to remove the clutch with the drive belt still on the car? the belt is only a couple of months old and doesn't need changing, so if it doesn't need to come off for this job, I won't disturb it.
 

kth286

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OK the test for fan fitness according to Merc workshop manual.

This for all 104 engines as fitted to a variety of cars including the 140 model.

Firstly, note, it can kick-in as late as 100 degrees.

The test is confirmed by noise.

Park car/bonnet up. Start and run engine at high revs until engine is as hot as it can get.

The fan must come on at around max 100 degrees.

When fan is activated it will give an almighty whoosh.

That is the test.

No whoosh = no lock-up of fan = fan faulty.
 

WDB124066

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Did you find the temp ranges for the 124 kth286, I remember looking at them with the Dealer here, they had a sheet will all the begin to engage and fully engaged temps and I remember distinctly these temp ranges for the 124 were higher than any other car with the 104 engine, 140, 129, 202 .....

The noise can be heard very clearly on the run with a new VC, in fact it’s too loud for my liking to be honest & together with not switching off till the mid to low 80's I had thought there was something wrong with it. Still think they should switch off a little earlier.

See how you get on with yours, I would be very interested to know if you find the noise a little overpowering and the temp at which the fan disengages a little low i.e. it struggles to switch off once on.......
 

Ian B Walker

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My 24valve has had a new Coupling fitted (gen Mb). Seems to cut in quite early and is quite noisy. Scares the local populace a bit, thinking the car is doing serious mph. But you learn to live with it. BTW the temperature never gets above 80 degrees. ( I may have a thermostat issue )
 

scillyisles

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Ermm is not the whoosh the electric auxiliary fans which are in front of the radiator kicking in. They are fitted to M104 cars with a/c or climate. They cutin when the temp rises to 90c or so. I have just had the viscous fan drive on mine replaced as the old one was kaput. I do not get a whoosh other than the electric fans.
 

kth286

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Ermm is not the whoosh the electric auxiliary fans which are in front of the radiator kicking in. They are fitted to M104 cars with a/c or climate. They cutin when the temp rises to 90c or so. I have just had the viscous fan drive on mine replaced as the old one was kaput. I do not get a whoosh other than the electric fans.

If you do not get the whoosh from viscous fan then perhaps enfgine not getting hot enough OR new fan was stored incorrectly on it's side.

Try isolating the electric fans and see just the effect of viscous fan.
 

Spinal

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It's not a W124, but you don't need special tools... just lock & give it a sharp whack to loosen it ;)

[youtube]z3ETTFeGhSs[/youtube]
[youtube]UYaEwfhfOG8[/youtube]
 

kth286

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we've already discussed - it's not that set-up on 104.

also with it being a longer 6 cylinder engine room is very difficult.
 
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millo777

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Thanks for your responses. All sorted now, and the new fan does come on with quite a whoosh.

@kth286, re the workshop test for the fan. The noise test makes perfect sense, and it was the noise of the fan kicking in that I kept expecting to happen when the car temp was risining in traffic, but never heard. The other tests were really to sanity check what I already suspected.

The actual process of changing the fan wasn't too bad. I opted to take the belt off first, mainly for fear of turning the ancillaies the wrong way and potentially dmaaging anything. In the end I managed to improvise using a strap type oil filter wrench to hold the fan pulley while loosening the hex nut holding the fan clutch in place.

The only annoyance was that having been promosed a sachs clutch from GSF when ordering, a brand I'd never heard of, "Flusser" arrived, and that point is was too late to find an alternative as I needed the car. Given more time I would have ordered an oem BEHR unit either form the dealer or elsewhere. This always seems to happen with GSF. Either the part doesn't fit, or it's not the make that was promised.

I also changed the thermostat, which having got the old one out and tested it was fine, so at least I have a spare if needed in the future. Strangely the oem BEHR thermostat was marked as 83c and the replacement as 88c.

In both cases the BEHR units looked and felt much much better made, so for anyone else doing the same jobs, I'd seriously recommend spending a little more and getting the oem brand.
 

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