News:

www.W116.org
All about the Car!

Main Menu

Fan clutch musings

Started by daantjie, 04 May 2022, 11:22 AM

daantjie

Hi guys

Looking at the 6.9 fan clutch, the replacement units now seem way less robust than the original unit.  I swapped mine out for a Behr unit which I'm sure is likely garbage compared to the Benz units which are long since NLA.

It seems very stiff to turn when cold, and does seem to run even with cold engine so methinks it is likely faulty out of the box?

Any thoughts?
Cheers
Daniel
1977 450 SEL 6.9 - Astralsilber

johnnyw116

i have a Mahle-Behr CFC81000P replacement this one is also stiff when cold , i heard from some mechanics in the past that it's normal that the clutch runs for a short moment when cold   
JohnnyW116

daantjie

Quote from: johnnyw116 on 05 May 2022, 06:02 AMi have a Mahle-Behr CFC81000P replacement this one is also stiff when cold , i heard from some mechanics in the past that it's normal that the clutch runs for a short moment when cold   

Indeed yes but mine keeps running from start and does not seem to slow down.
Daniel
1977 450 SEL 6.9 - Astralsilber

johnnyw116

#3
No if it keeps running it can't be good , mine runs for about 5/6 minutes when cold
JohnnyW116

daantjie

Quote from: johnnyw116 on 05 May 2022, 10:25 AMNo if it keeps running it can't be good , mine runs for about 5/6 minutes when cold

Yes my understanding is that from cold it should run steadily for a short while at approximately engine speed then taper off.  Then depending on air flow across the unit it will kick on and then again run at engine speed until you get to about 3500 rpm whereafter it should decouple until the revs drop again and then kick on again.
Mine roars up with engine revs from cold which does not seem right.
Daniel
1977 450 SEL 6.9 - Astralsilber

ptashek

Quote from: daantjie on 05 May 2022, 04:49 PM
Quote from: johnnyw116 on 05 May 2022, 10:25 AMNo if it keeps running it can't be good , mine runs for about 5/6 minutes when cold

Yes my understanding is that from cold it should run steadily for a short while at approximately engine speed then taper off.  Then depending on air flow across the unit it will kick on and then again run at engine speed until you get to about 3500 rpm whereafter it should decouple until the revs drop again and then kick on again.
Mine roars up with engine revs from cold which does not seem right.

Mine does that too. It's perfectly normal I guess as the car warms up well, and quick, and holds temperature rock solid no matter what.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

rumb

The little blue book has specs on this. I recall the 6 9 is different than others. Not home at the moment to look.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS

daantjie

Quote from: rumb on 06 May 2022, 06:53 AMThe little blue book has specs on this. I recall the 6 9 is different than others. Not home at the moment to look.

Interesting...please let me know cheers.
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

Golden oldie post of mine:

03 October 2017, 01:40 PM
Having just replaced my fan clutch and reading the 100-985 manual

up to a speed of 3500 rpm the fan will run proportional to the engine speed, whereby a fan speed of 1900 rpm results

as engine speed increases further the fan speed will drop to about 1000 rpm and max of 1200

It should be very stiff when cold. if it freewheels at all it's shot.


Testing:
increase engine speed slowly, fan speed must drop, which is heard clearly at a maximal speed of 3500 rpm

Also make sure you are using a 87 degree thermostat.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS

daantjie

Quote from: rumb on 07 May 2022, 06:10 PMGolden oldie post of mine:

03 October 2017, 01:40 PM
Having just replaced my fan clutch and reading the 100-985 manual

up to a speed of 3500 rpm the fan will run proportional to the engine speed, whereby a fan speed of 1900 rpm results

as engine speed increases further the fan speed will drop to about 1000 rpm and max of 1200

It should be very stiff when cold. if it freewheels at all it's shot.


Testing:
increase engine speed slowly, fan speed must drop, which is heard clearly at a maximal speed of 3500 rpm

Also make sure you are using a 87 degree thermostat.


Cool ;)   I also read in the M100 engine manual it calls for a 100kpa radiator cap.  Not sure if it matters much but I know you get 120 and 140 kpa ones for Benz.
Daniel
1977 450 SEL 6.9 - Astralsilber